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[Emacs-diffs] feature/new-tutorial 1f5d3b7 04/10: Add test framework


From: Phillip Lord
Subject: [Emacs-diffs] feature/new-tutorial 1f5d3b7 04/10: Add test framework
Date: Thu, 18 May 2017 05:18:53 -0400 (EDT)

branch: feature/new-tutorial
commit 1f5d3b70abe61bb50e846cde5eb1f9b25effc6e2
Author: Phillip Lord <address@hidden>
Commit: Phillip Lord <address@hidden>

    Add test framework
---
 lisp/emacs-lisp/assess/assess-call.el      |  115 +++
 lisp/emacs-lisp/assess/assess-discover.el  |   87 ++
 lisp/emacs-lisp/assess/assess-robot.el     |  111 +++
 lisp/emacs-lisp/assess/assess.el           | 1176 ++++++++++++++++++++++++++++
 lisp/emacs-lisp/m-buffer/m-buffer-at.el    |   89 +++
 lisp/emacs-lisp/m-buffer/m-buffer-macro.el |  123 +++
 lisp/emacs-lisp/m-buffer/m-buffer-pkg.el   |    2 +
 lisp/emacs-lisp/m-buffer/m-buffer.el       |  984 +++++++++++++++++++++++
 test/lisp/tutorial-tests.el                |   43 +
 9 files changed, 2730 insertions(+)

diff --git a/lisp/emacs-lisp/assess/assess-call.el 
b/lisp/emacs-lisp/assess/assess-call.el
new file mode 100644
index 0000000..78d6174
--- /dev/null
+++ b/lisp/emacs-lisp/assess/assess-call.el
@@ -0,0 +1,115 @@
+;;; assess-call.el --- Call and Return -*- lexical-binding: t -*-
+
+;;; Header:
+
+;; This file is not part of Emacs
+
+;; Author: Phillip Lord <address@hidden>
+;; Maintainer: Phillip Lord <address@hidden>
+
+;; The contents of this file are subject to the GPL License, Version 3.0.
+
+;; Copyright (C) 2016, Phillip Lord
+
+;; This program is free software: you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation, either version 3 of the License, or
+;; (at your option) any later version.
+
+;; This program is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;; GNU General Public License for more details.
+
+;; You should have received a copy of the GNU General Public License
+;; along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+;;; Commentary:
+
+;; Capture calls to functions, checking parameters and return values.
+
+;;; Code:
+
+;; ** Call Capture
+
+;; Here we provide a function for tracing calls to a particular function. This
+;; can be a direct or indirect call; parameters and return values are available
+;; for inspection afterwards. For example:
+
+;; #+begin_src elisp
+;;   (assess-call-capture
+;;     '+
+;;     (lambda()
+;;       (+ 1 1)))
+;;   ;; => (((1 1) . 2))
+;; #+end_src
+
+;; The return value is a list of cons cells, one for each invocation, of the
+;; parameters and return values.
+
+
+;; #+begin_src emacs-lisp
+(defun assess-call--capture-lambda ()
+  "Return function which captures args and returns of another.
+
+The returned function takes FN the function to call, and any
+number of ARGS to call the function with. In the special case,
+that FN is equal to `:return`, then all previous args and return
+values of FN are returned instead."
+  (let ((capture-store nil))
+    (lambda (fn &rest args)
+      (if (eq fn :return)
+          capture-store
+        (let ((rtn (apply fn args)))
+          (setq capture-store
+                (cons (cons args rtn)
+                      capture-store))
+          rtn)))))
+
+(defun assess-call-capture (sym-fn fn)
+  "Trace all calls to SYM-FN when FN is called with no args.
+
+The return value is a list of cons cells, with car being the
+parameters of the calls, and the cdr being the return value."
+  (let ((capture-lambda
+         (assess-call--capture-lambda)))
+    (unwind-protect
+        (progn (advice-add sym-fn :around capture-lambda)
+               (funcall fn)
+               (funcall capture-lambda :return))
+      (advice-remove sym-fn capture-lambda))))
+
+(defun assess-call--hook-capture-lambda ()
+  "Returns a function which captures all of its args.
+
+The returned function takes any number of ARGS. In the special
+case that the first arg is `:return` then it returns all previous
+args."
+  (let ((capture-store nil))
+    (lambda (&rest args)
+      (if (eq (car-safe args) :return)
+          capture-store
+        (setq capture-store
+              (cons
+               args
+               capture-store))))))
+
+(defun assess-call-capture-hook (hook-var fn &optional append local)
+  "Trace all calls to HOOK-VAR when FN is called with no args.
+APPEND and LOCAL are passed to `add-hook` and documented there."
+  (let ((capture-lambda
+         (assess-call--hook-capture-lambda)))
+    (unwind-protect
+        (progn
+          (add-hook hook-var
+                    capture-lambda
+                    append local)
+          (funcall fn)
+          (funcall capture-lambda :return))
+      (remove-hook hook-var
+                   capture-lambda
+                   local))))
+
+(provide 'assess-call)
+;;; assess-call.el ends here
+;; #+end_src
diff --git a/lisp/emacs-lisp/assess/assess-discover.el 
b/lisp/emacs-lisp/assess/assess-discover.el
new file mode 100644
index 0000000..51cabb2
--- /dev/null
+++ b/lisp/emacs-lisp/assess/assess-discover.el
@@ -0,0 +1,87 @@
+;;; assess-discover.el --- Test support functions -*- lexical-binding: t -*-
+
+;;; Header:
+
+;; This file is not part of Emacs
+
+;; Author: Phillip Lord <address@hidden>
+;; Maintainer: Phillip Lord <address@hidden>
+
+;; The contents of this file are subject to the GPL License, Version 3.0.
+
+;; Copyright (C) 2015, 2016, Phillip Lord
+
+;; This program is free software: you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation, either version 3 of the License, or
+;; (at your option) any later version.
+
+;; This program is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;; GNU General Public License for more details.
+
+;; You should have received a copy of the GNU General Public License
+;; along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+;;; Code:
+
+
+;; #+begin_src emacs-lisp
+(defun assess-discover-tests (directory)
+  "Discover tests in directory.
+
+Tests must conform to one (and only one!) of several naming
+schemes.
+
+ - End with -test.el
+ - End with -tests.el
+ - Start with test-
+ - Any .el file in a directory called test
+ - Any .el file in a directory called tests
+
+Each of these is tried until one matches. So, a top-level file
+called \"blah-test.el\" will prevent discovery of files in a
+tests directory."
+  (or
+   ;; files with
+   (directory-files directory nil ".*-test.el$")
+   (directory-files directory nil ".*-tests.el$")
+   (directory-files directory nil "test-.*.el$")
+   (let ((dir-test
+          (concat directory "test/")))
+     (when (file-exists-p dir-test)
+       (mapcar
+        (lambda (file)
+          (concat dir-test file))
+        (directory-files dir-test nil ".*.el"))))
+   (let ((dir-tests
+          (concat directory "tests/")))
+     (when (file-exists-p dir-tests)
+       (mapcar
+        (lambda (file)
+          (concat dir-tests file))
+        (directory-files dir-tests nil ".*.el"))))))
+
+(defun assess-discover--load-all-tests (directory)
+  (mapc
+   'load
+   (assess-discover-tests directory)))
+
+(defun assess-discover-load-tests ()
+  (interactive)
+  (assess-discover--load-all-tests default-directory))
+
+;;;###autoload
+(defun assess-discover-run-batch (&optional selector)
+  (assess-discover--load-all-tests default-directory)
+  (ert-run-tests-batch selector))
+
+;;;###autoload
+(defun assess-discover-run-and-exit-batch (&optional selector)
+  (assess-discover--load-all-tests default-directory)
+  (ert-run-tests-batch-and-exit selector))
+
+(provide 'assess-discover)
+;;; assess-discover.el ends here
+;; #+end_src
diff --git a/lisp/emacs-lisp/assess/assess-robot.el 
b/lisp/emacs-lisp/assess/assess-robot.el
new file mode 100644
index 0000000..45ff0e2
--- /dev/null
+++ b/lisp/emacs-lisp/assess/assess-robot.el
@@ -0,0 +1,111 @@
+;;; assess-robot.el --- Test support functions -*- lexical-binding: t -*-
+
+;;; Header:
+
+;; This file is not part of Emacs
+
+;; Author: Phillip Lord <address@hidden>
+;; Maintainer: Phillip Lord <address@hidden>
+;; Version: 0.2
+
+;; The contents of this file are subject to the GPL License, Version 3.0.
+
+;; Copyright (C) 2016, Phillip Lord
+
+;; This program is free software: you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation, either version 3 of the License, or
+;; (at your option) any later version.
+
+;; This program is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;; GNU General Public License for more details.
+
+;; You should have received a copy of the GNU General Public License
+;; along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+;;; Code:
+(defmacro assess-robot-with-switched-buffer (buffer &rest body)
+  "With BUFFER, evaluate BODY.
+
+This macro is rather like `with-current-buffer', except that it
+uses `switch-to-buffer'. This is generally a bad idea when used
+programmatically. But, it is necessary, for example, when using
+keyboard macros."
+  (declare (indent 1) (debug t))
+  (let ((before-buffer (make-symbol "before-buffer")))
+    `(let ((,before-buffer (current-buffer)))
+       (unwind-protect
+           (progn
+             (switch-to-buffer ,buffer)
+             ,@body)
+         (switch-to-buffer ,before-buffer)))))
+
+(defmacro assess-robot-with-temp-switched-buffer (&rest body)
+  "Evaluate BODY in temporary buffer.
+
+As with `assess-robot-with-switched-buffer', `switch-to-buffer'
+is used."
+  (declare (indent 0) (debug t))
+  (let ((temp-buffer (make-symbol "temp-buffer")))
+    `(let ((,temp-buffer (generate-new-buffer " *temp*")))
+       (assess-robot-with-switched-buffer ,temp-buffer
+         (unwind-protect
+             (progn
+               ;; Enable the undo list because we want it for most robot
+               ;; situations.
+               (setq buffer-undo-list nil)
+               ,@body)
+           (and (buffer-name ,temp-buffer)
+                (kill-buffer ,temp-buffer)))))))
+
+(defmacro assess-robot-with-switched-buffer-string (&rest body)
+  "Evalate BODY in a temporary buffer and return buffer string.
+
+See also `assess-robot-with-temp-switched-buffer'."
+  (declare (debug t))
+  `(assess-robot-with-temp-switched-buffer
+     (progn
+       ,@body
+       (buffer-substring-no-properties
+        (point-min) (point-max)))))
+
+(defun assess-robot-execute-kmacro (macro)
+  "Execute the MACRO.
+
+In this case, MACRO is the \"long form\" accepted by
+`edit-kdb-macro'."
+  (let ((macro (read-kbd-macro macro)))
+    ;; I wanted to add a nice way to edit the macro, but sadly
+    ;; edit-kdb-macro provides no nice entry point. So, we take the nasty step
+    ;; of setting the last-kbd-macro instead.
+    (setq last-kbd-macro macro)
+    (execute-kbd-macro
+     (read-kbd-macro macro))))
+
+(defun assess-robot-copy-and-finish ()
+  "Copy the macro in edmacro to the kill-ring."
+  (interactive)
+  (save-excursion
+    (goto-char (point-min))
+    (search-forward "Macro:")
+    (forward-line)
+    (let ((string
+           (buffer-substring-no-properties
+            (point)
+            (point-max))))
+      (with-temp-buffer
+        (insert "\"")
+        (insert string)
+        (insert "\"")
+        (kill-ring-save (point-min)
+                        (point-max))))
+    (edmacro-finish-edit)))
+
+(eval-after-load
+    'edmacro
+  '(define-key edmacro-mode-map (kbd "C-c C-k") 'assess-robot-copy-and-finish))
+
+(provide 'assess-robot)
+;;; assess-robot.el ends here
diff --git a/lisp/emacs-lisp/assess/assess.el b/lisp/emacs-lisp/assess/assess.el
new file mode 100644
index 0000000..9866899
--- /dev/null
+++ b/lisp/emacs-lisp/assess/assess.el
@@ -0,0 +1,1176 @@
+;;; assess.el --- Test support functions -*- lexical-binding: t -*-
+
+;;; Header:
+
+;; This file is not part of Emacs
+
+;; Author: Phillip Lord <address@hidden>
+;; Maintainer: Phillip Lord <address@hidden>
+;; Version: 0.4
+;; Package-Requires: ((emacs "24.1")(m-buffer "0.15"))
+
+;; The contents of this file are subject to the GPL License, Version 3.0.
+
+;; Copyright (C) 2015, 2016, Phillip Lord
+
+;; This program is free software: you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation, either version 3 of the License, or
+;; (at your option) any later version.
+
+;; This program is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;; GNU General Public License for more details.
+
+;; You should have received a copy of the GNU General Public License
+;; along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+;;; Commentary:
+
+;; This file provides functions to support ert, the Emacs Regression Test
+;; framework. It includes:
+
+;;  - a set of predicates for comparing strings, buffers and file contents.
+;;  - explainer functions for all predicates giving useful output
+;;  - macros for creating many temporary buffers at once, and for restoring the
+;;    buffer list.
+;;  - methods for testing indentation, by comparison or "round-tripping".
+;;  - methods for testing fontification.
+
+;; Assess aims to be a stateless as possible, leaving Emacs unchanged whether
+;; the tests succeed or fail, with respect to buffers, open files and so on; 
this
+;; helps to keep tests independent from each other. Violations of this will be
+;; considered a bug.
+
+;; Assess aims also to be as noiseless as possible, reducing and suppressing
+;; extraneous messages where possible, to leave a clean ert output in batch 
mode.
+
+
+;;; Status:
+
+;; Assess is currently a work in progress; the API is not currently stable. I
+;; may also considering winding this into ert-x, because then it can be used
+;; to test core.
+
+;; Assess used to be called sisyphus which seemed like a good idea when I
+;; started, but I kept spelling it wrong.
+
+
+;;; Code:
+
+;; ** Preliminaries
+
+;; #+begin_src emacs-lisp
+(require 'pp)
+(require 'ert)
+(require 'm-buffer-at)
+(require 'm-buffer)
+(require 'seq)
+;; #+end_src
+
+;; ** Advice
+
+;; Emacs-24 insists on printing out results on a single line with escaped
+;; newlines. This does not work so well with the explainer functions in assess
+;; and, probably, does not make sense anywhere. So, we advice here. The use of
+;; nadvice.el limits this package to Emacs 24.4. Emacs 25 has this fixed.
+
+;; #+begin_src emacs-lisp
+(when (fboundp 'advice-add)
+
+  (defun assess--ert-pp-with-indentation-and-newline (orig object)
+    (let ((pp-escape-newlines nil))
+      (funcall orig object)))
+
+  (advice-add
+   'ert--pp-with-indentation-and-newline
+   :around
+   #'assess--ert-pp-with-indentation-and-newline))
+;; #+end_src
+
+;; ** Deliberate Errors
+
+;; Sometimes during testing, we need to throw an "error" deliberately. Assess'
+;; own test cases do this to check that state is preserved with this form of
+;; non-local exit. Throwing `error' itself is a bit dangerous because we might
+;; get that for other reasons; so we create a new symbol here for general use.
+
+;; #+begin_src emacs-lisp
+(if (fboundp 'define-error)
+    (define-error 'assess-deliberate-error
+      "An error deliberately caused during testing."
+      'error)
+  (put 'assess-deliberate-error
+       'error-conditions
+       '(error assess-deliberate-error))
+  (put 'assess-deliberate-error
+       'error-message
+       "A error deliberately caused during testing."))
+;; #+end_src
+
+;; ** Buffer creation
+
+;; For tests, it is often better to use temporary buffers, as it is much less
+;; affected by the existing state of Emacs, and much less likely to affect 
future
+;; state; this is particularly the case where tests are being developed as the
+;; developer may be trying to change or write test files at the same time as
+;; Emacs is trying to use them for testing.
+
+;; Emacs really only provides a single primitive `with-temp-buffer' for this
+;; situation, and that only creates a single temporary buffer at a time. 
Nesting
+;; of these forms sometimes works, but fails if we need to operate on two 
buffers
+;; at once.
+
+;; So, we provide an environment for restoring the buffer list. This allows any
+;; creation of buffers we need for testing, followed by clean up afterwards. 
For
+;; example, a trivial usage would be to remove buffers explicitly created.
+
+;; #+begin_src elisp
+;;   (assess-with-preserved-buffer-list
+;;    (get-buffer-create "a")
+;;    (get-buffer-create "b")
+;;    (get-buffer-create "c"))
+;; #+end_src
+
+;; Any buffer created in this scope is removed, whether this is as a direct or
+;; indirect result of the function. For example, this usage creates a ~*Help*~
+;; buffer which then gets removed again.
+
+;; #+begin_src elisp
+;;   (assess-with-preserved-buffer-list
+;;    (describe-function 'self-insert-command))
+;; #+end_src
+
+;; This does not prevent changes to existing buffers of course. If ~*Help*~ is
+;; already open before evaluation, it will remain open afterwards but with
+;; different content.
+
+;; Sometimes, it is useful to create several temporary buffers at once.
+;; `assess-with-temp-buffers' provides an easy mechanism for doing this, as
+;; well as evaluating content in these buffers. For example, this returns true
+;; (actually three killed buffers which were live when the `mapc' form runs).
+
+;; #+begin_src elisp
+;;   (assess-with-temp-buffers
+;;       (a b c)
+;;     (mapc #'buffer-live-p (list a b c)))
+;; #+end_src
+
+;; While this creates two buffers, puts "hellogoodbye" into one and "goodbye"
+;; into the other, then compares the contents of these buffers with `assess='.
+
+;; #+begin_src elisp
+;;   (assess-with-temp-buffers
+;;       ((a (insert "hello")
+;;           (insert "goodbye"))
+;;        (b (insert "goodbye")))
+;;     (assess= a b))
+;; #+end_src
+
+;; Finally, we provide a simple mechanism for converting any assess type into a
+;; buffer. The following form, for example, returns the contents of the 
~.emacs~
+;; file.
+
+;; #+begin_src elisp
+;;   (assess-as-temp-buffer
+;;       (assess-file "~/.emacs")
+;;     (buffer-string))
+;; #+end_src
+
+;; *** Implementation
+
+;; #+begin_src emacs-lisp
+(defmacro assess-with-preserved-buffer-list (&rest body)
+  "Evaluate BODY, but delete any buffers that have been created."
+  (declare (debug t))
+  `(let ((before-buffer-list
+          (buffer-list)))
+     (unwind-protect
+         (progn
+           ,@body)
+       (seq-map
+        (lambda (it)
+          (with-current-buffer it
+            (set-buffer-modified-p nil)
+            (kill-buffer)))
+        (seq-difference (buffer-list)
+                        before-buffer-list)))))
+
+(defun assess--temp-buffer-let-form (item)
+  (if (not (listp item))
+      (assess--temp-buffer-let-form
+       (list item))
+    `(,(car item)
+      (with-current-buffer
+          (generate-new-buffer " *assess-with-temp-buffers*")
+        ,@(cdr item)
+        (current-buffer)))))
+;; #+end_src
+
+;; The implementation of `assess-with-temp-buffers' currently uses
+;; `assess-with-preserved-buffer-list' to remove buffers which means that it
+;; will also delete any buffers created by the user; this may be a mistake, and
+;; it might be better to delete the relevant buffers explicitly.
+
+;; #+begin_src emacs-lisp
+(defmacro assess-with-temp-buffers (varlist &rest body)
+  "Bind variables in varlist to temp buffers, then eval BODY.
+
+VARLIST is (nearly) of the same form as a `let' binding. Each
+element is a symbol or a list (symbol valueforms). Each symbol is
+bound to a buffer generated with `generate-new-buffer'.
+VALUEFORMS are evaluated with the buffer current. Any buffers
+created inside this form (and not just by this form!) are
+unconditionally killed at the end of the form.
+
+Unlike `let' there can be multiple valueforms which are,
+effectively, placed within an impicit `progn'."
+  (declare (indent 1)
+           (debug
+            ((&rest (symbolp &rest form))
+             body)))
+  (let ((let-form
+         (seq-map
+          #'assess--temp-buffer-let-form
+          varlist)))
+    `(assess-with-preserved-buffer-list
+      (let* ,let-form
+        ,@body))))
+
+(defmacro assess-as-temp-buffer (x &rest body)
+  "Insert X in a type-appropriate way into a temp buffer and eval
+BODY there.
+
+See `assess-to-string' for the meaning of type-appropriate."
+  (declare (indent 1) (debug t))
+  `(with-temp-buffer
+     (insert (assess-to-string ,x))
+     ,@body))
+;; #+end_src
+
+;; ** Types
+
+;; Many tests on files or buffers actually end up being string comparison.
+;; In many cases, we want to compare the *contents* of a buffer to, for 
example,
+;; the *contents* of a file.
+
+;; Emacs normally uses strings to represent files (i.e. file names) and can 
also
+;; use them to represent buffers (i.e. buffer names). So, here, we introduce a
+;; set of "types" where so that we can distinguish between strings, buffer 
names
+;; and file names, passing them at a single parameter. This will allow us to 
make
+;; later parts of the API use overloaded methods based on their type.
+
+;; "Types" are either a Emacs core type (as with buffers and strings), or an 2
+;; element list (I haven't used cons cells in case I want to add more 
elements),
+;; with a keyword at the head. This allows assess to distinguish between a
+;; simple string and a file or buffer name.
+
+;; #+begin_src elisp
+;; ;; Identify "~/.emacs" as a file name
+;; (assess-file "~/.emacs")
+
+;; ;; Identify "*Messages*" as a buffer
+;; (assess-buffer "*Messages*")
+;; #+end_src
+
+;; *** Implementation
+
+;; #+begin_src emacs-lisp
+(defun assess-to-string (x)
+  "Turn X into a string in a type appropriate way.
+
+If X is identified as a file, returns the file contents.
+If X is identified as a buffer, returns the buffer contents.
+If X is a string, returns that.
+
+See also `assess-buffer' and `assess-file' which turn a
+string into something that will identified appropriately."
+  (pcase x
+    ((pred stringp) x)
+    ((pred bufferp) (m-buffer-at-string x))
+    (`(:buffer ,b) (assess-to-string (get-buffer-create b)))
+    (`(:file ,f)
+     (with-temp-buffer
+       (insert-file-contents f)
+       (buffer-string)))
+    ;; error condition
+    (_ (error "Type not recognised"))))
+
+(defun assess-buffer (b)
+  "Add type data to the string B marking it as a buffer."
+  `(:buffer ,b))
+
+(defun assess-file (f)
+  "Add type data to the string F marking it as a file."
+  `(:file ,f))
+
+(defun assess-to-file-name (file)
+  "Return file name for FILE.
+
+FILE can be either a string, or a plist returned by
+`assess-file' or `assess-make-related-file'."
+  (pcase file
+    ((pred stringp) file)
+    (`(:file ,f) f)
+    (_ (error "Type not recognised"))))
+;; #+end_src
+
+;; ** Entity Comparison
+
+;; In this section, we provide support for comparing strings, buffer or file
+;; contents. The main entry point is `assess=', which works like `string=' but
+;; on any of the three data types, in any order.
+
+;; #+begin_src elisp
+;;   ;; Compare Two Strings
+;;   (assess= "hello" "goodbye")
+
+;;   ;; Compare the contents of Two Buffers
+;;   (assess=
+;;    (assess-buffer "assess.el")
+;;    (assess-buffer "assess-previous.el"))
+
+;;   ;; Compare the contents of Two files
+;;   (assess=
+;;    (assess-file "~/.emacs")
+;;    (assess-file "~/.emacs"))
+
+;;   ;; We can use core Emacs types also
+;;   (assess=
+;;    (assess-buffer "assess.el")
+;;    (get-buffer "assess-previous.el"))
+
+;;   ;; And in any combination; here we compare a string and the contents of a
+;;   ;; file.
+;;   (assess=
+;;    ";; This is an empty .emacs file"
+;;    (assess-file "~/.emacs"))
+;; #+end_src
+
+;; In addition, `assess=' has an "explainer" function attached which produces a
+;; richer output when `assess=' returns false, showing diffs of the string
+;; comparison. Compare, for example, the results of running these two tests, 
one
+;; using `string=' and one using `assess='.
+
+;; #+BEGIN_EXAMPLE
+;; F temp
+;;     (ert-test-failed
+;;      ((should
+;;        (string= "a" "b"))
+;;       :form
+;;       (string= "a" "b")
+;;       :value nil))
+
+;; F test-assess=
+;;     (ert-test-failed
+;;      ((should
+;;        (assess= "a" "b"))
+;;       :form
+;;       (assess= "a" "b")
+;;       :value nil :explanation "Strings:
+;; a
+;; and
+;; b
+;; Differ at:*** /tmp/a935uPW  2016-01-20 13:25:47.373076381 +0000
+;; --- /tmp/b9357Zc    2016-01-20 13:25:47.437076381 +0000
+;;  ***************
+;;  *** 1 ****
+;; ! a
+;; \\ No newline at end of file
+;; --- 1 ----
+;; ! b
+;; \\ No newline at end of file
+
+;; "))
+;; #+END_EXAMPLE
+
+;; As `assess=' has a compatible interface with `string=' it is also possible
+;; to add this explainer function to `string=' for use with tests which do not
+;; otherwise use assess, like so:
+
+;; #+begin_src elisp
+;; (put 'string= 'ert-explainer 'assess-explain=)
+;; #+end_src
+
+;; Currently, `assess' uses the ~diff~ program to do the comparison if it is
+;; available, or falls back to just reporting a difference -- this could do 
with
+;; improving, but it is at least no worse than the existing behaviour for 
string
+;; comparison.
+
+;; *** Implementation
+
+;; We start by writing a file silently -- this is important because the
+;; ~*Messages*~ buffer should not be affected by the machinary of a failing 
test,
+;; as it hides what is happening from the test code.
+
+;; #+begin_src emacs-lisp
+(defun assess--write-file-silently (filename)
+  "Write current buffer into FILENAME.
+Unlike most other ways of saving a file, this should not
+print any messages!"
+  (write-region
+   (point-min) (point-max)
+   filename nil
+   'dont-display-wrote-file-message))
+;; #+end_src
+
+;; Diff does a nicer comparison than anything in Emacs, although a lisp
+;; implementation would have been more portable. Diff is used by quite a few
+;; other tools in Emacs, so probably most people will have access to diff.
+
+;; #+begin_src emacs-lisp
+(defun assess--explainer-diff-string= (a b)
+  "Compare strings A and B using diff output.
+
+We assume that diff exists. Temporary files are left
+afterwards for cleanup by the operating system."
+  (assess-with-preserved-buffer-list
+   (let* ((diff
+           (executable-find "diff"))
+          (a-buffer
+           (generate-new-buffer "a"))
+          (b-buffer
+           (generate-new-buffer "b"))
+          (a-file
+           (make-temp-file
+            (buffer-name a-buffer)))
+          (b-file
+           (make-temp-file
+            (buffer-name b-buffer))))
+     (with-current-buffer
+         a-buffer
+       (insert a)
+       (assess--write-file-silently a-file))
+     (with-current-buffer
+         b-buffer
+       (insert b)
+       (assess--write-file-silently b-file))
+     (progn
+         (format "Strings:\n%s\nand\n%s\nDiffer at:%s\n"
+                 a b
+                 (with-temp-buffer
+                   (call-process
+                    diff
+                    ;; no infile
+                    nil
+                    ;; dump to current buffer
+                    t
+                    nil
+                    "-c"
+                    a-file
+                    b-file)
+                   (buffer-string)))))))
+
+(defun assess--explainer-simple-string= (a b)
+  "Compare strings for first difference."
+  ;; We could do a bit more here.
+  (format "String :%s:%s: are not equal." a b))
+;; #+end_src
+
+;; And the actual predicate function and explainer. We do a simple string
+;; comparison on the contents of each entity.
+
+;; #+begin_src emacs-lisp
+(defun assess= (a b)
+  "Compare A and B to see if they are the same.
+
+Equality in this sense means compare the contents in a way which
+is appropriate for the type of the two arguments. So, if they are
+strings, the compare strings, if buffers, then compare the buffer
+contents and so on.
+
+Text properties in strings or buffers are ignored."
+  (string=
+   (assess-to-string a)
+   (assess-to-string b)))
+
+(defun assess-explain= (a b)
+  "Compare A and B and return an explanation.
+
+This function is called by ERT as an explainer function
+automatically. See `assess=' for more information."
+  (let ((a (assess-to-string a))
+        (b (assess-to-string b)))
+    (cond
+     ((assess= a b)
+      t)
+     ((executable-find "diff")
+      (assess--explainer-diff-string= a b))
+     (t
+      (assess--explainer-simple-string= a b)))))
+
+(put 'assess= 'ert-explainer 'assess-explain=)
+;; #+end_src
+
+;; ** Opening files
+
+;; Opening files presents a particular problem for testing, particularly if we
+;; open a file that is already open in the same or a different Emacs. For batch
+;; use of Emacs with parallelisation, the situation becomes intractable.
+
+;; A solution is to copy files before we open them, which means that they can 
be
+;; changed freely. Largely, the copied file will behave the same as the main 
file;
+;; the only notable exception to this is those features which depend on the
+;; current working directory (dir-local variables, for example).
+
+;; ~assess-make-related-file~ provides a simple method for doing this. For
+;; example, this form will return exactly the contents of ~my-test-file.el~, 
even
+;; if that file is current open in the current Emacs (even if the buffer has 
not
+;; been saved). Likewise, a test opening this file could be run in a batch 
Emacs
+;; without interfering with an running interactive Emacs.
+
+;; #+begin_src elisp
+;;   (assess-as-temp-buffer
+;;       (assess-make-related-file "dev-resources/my-test-file.el")
+;;     (buffer-substring))
+;; #+end_src
+
+;; We also add support for opening a file, as if it where opened interactively,
+;; with all the appropriate hooks being run, in the form of the
+;; `assess-with-find-file' macro. Combined with `assess-make-related-file',
+;; we can write the following expression without removing our ~.emacs~.
+
+;; #+begin_src elisp
+;;   (assess-with-find-file
+;;       (assess-make-related-file "~/.emacs")
+;;     (erase-buffer)
+;;     (save-buffer))
+;; #+end_src
+
+;; #+RESULTS:
+
+;; *** Implementation
+
+;; All of the functions here support the file type introduced earlier, but
+;; interpret raw strings as a file also.
+
+;; #+begin_src emacs-lisp
+(defun assess--make-related-file-1 (file &optional directory)
+  (make-temp-file
+   (concat
+    (or directory
+        temporary-file-directory)
+    (file-name-nondirectory file))
+   nil
+   (concat "."
+           (file-name-extension file))))
+
+(defun assess-make-related-file (file &optional directory)
+  "Open a copy of FILE in DIRECTORY.
+
+FILE is copied to a temporary file in DIRECTORY or
+`temporary-file-directory'. The copy has a unique name but shares
+the same file extension.
+
+This is useful for making test changes to FILE without actually
+altering it."
+  (let* ((file (assess-to-file-name file))
+         (related-file
+          (assess--make-related-file-1 file directory)))
+    (copy-file file related-file t)
+    (assess-file
+     related-file)))
+
+(defmacro assess-with-find-file (file &rest body)
+  "Open FILE and evaluate BODY in resultant buffer.
+
+FILE is opened with `find-file-noselect' so all the normal hooks
+for file opening should occur. The buffer is killed after the
+macro exits, unless it was already open. This happens
+unconditionally, even if the buffer has changed.
+
+See also `assess-make-related-file'."
+  (declare (debug t) (indent 1))
+  (let ((temp-buffer (make-symbol "temp-buffer"))
+        (file-has-buffer-p (make-symbol "file-has-buffer-p"))
+        (file-s (make-symbol "file")))
+    `(let* ((,file-s ,file)
+            (,file-s (assess-to-file-name ,file-s))
+            (,file-has-buffer-p
+             (find-buffer-visiting ,file-s))
+            (,temp-buffer))
+       (unwind-protect
+           (with-current-buffer
+               (setq ,temp-buffer
+                     (find-file-noselect ,file-s))
+             ,@body)
+         (when
+          ;; kill the buffer unless it was already open.
+             (and (not ,file-has-buffer-p)
+                  (buffer-live-p ,temp-buffer))
+           ;; kill unconditionally
+           (with-current-buffer ,temp-buffer
+             (set-buffer-modified-p nil))
+           (kill-buffer ,temp-buffer))))))
+;; #+end_src
+
+;; ** Creating Files and Directories
+;; I can write some documentation here if Phil wants to merge code below.
+;; *** Implementation
+;; #+BEGIN_SRC emacs-lisp
+(defun assess-with-filesystem--make-parent (spec path)
+  "If SPEC is a file name, create its parent directory rooted at PATH."
+  (save-match-data
+    (when (string-match "\\(.*\\)/" spec)
+      (make-directory (concat path "/" (match-string 1 spec)) t))))
+
+(defun assess-with-filesystem--init (spec &optional path)
+  "Interpret the SPEC inside PATH."
+  (setq path (or path "."))
+  (cond
+   ((listp spec)
+    (cond
+     ;; non-empty file
+     ((and (stringp (car spec))
+           (stringp (cadr spec)))
+      (when (string-match-p "/\\'" (car spec))
+        (error "Invalid syntax: `%s' - cannot create a directory with text 
content" (car spec)))
+      (assess-with-filesystem--make-parent (car spec) path)
+      (with-temp-file (concat path "/" (car spec))
+        (insert (cadr spec))))
+     ;; directory
+     ((and (stringp (car spec))
+           (consp (cadr spec)))
+      (make-directory (concat path "/" (car spec)) t)
+      (mapc (lambda (s) (assess-with-filesystem--init
+                    s (concat path "/" (car spec)))) (cadr spec)))
+     ;; recursive spec, this should probably never happen
+     (t (mapc (lambda (s) (assess-with-filesystem--init s path)) spec))))
+   ;; directory specified using a string
+   ((and (stringp spec)
+         (string-match-p "/\\'" spec))
+    (make-directory (concat path "/" spec) t))
+   ;; empty file
+   ((stringp spec)
+    (assess-with-filesystem--make-parent spec path)
+    (write-region "" nil (concat path "/" spec) nil 'no-message))
+   (t (error "Invalid syntax: `%s'" spec))))
+
+(defmacro assess-with-filesystem (spec &rest forms)
+  "Create temporary file hierarchy according to SPEC and run FORMS.
+
+SPEC is a list of specifications for file system entities which
+are to be created.
+
+File system entities are specified as follows:
+
+1. a string FILE is the name of file to be created
+  - if the string contains \"/\", parent directories are created
+    automatically
+  - if the string ends with \"/\", a directory is created
+2. a list of two elements (FILE CONTENT) specifies filename and the
+  content to put in the file
+  - the \"/\" rules apply in the same way as in 1., except you can not
+    create a directory this way
+3. a list where car is a string and cadr is a list (DIR SPEC) is a
+  recursive specification evaluated with DIR as current directory
+  - the \"/\" rules apply in the same way as in 1., except you can not
+    create a file this way, a directory is always created
+
+An example showing all the possibilities:
+
+  (\"empty_file\"
+   \"dir/empty_file\"
+   \"dir/subdir/\"
+   (\"non_empty_file\" \"content\")
+   (\"dir/anotherdir/non_empty_file\" \"tralala\")
+   (\"big_dir\" (\"empty_file\"
+              (\"non_empty_file\" \"content\")
+              \"subdir/empty_file\")))
+
+If we want to run some code in a directory with an empty file
+\"foo.txt\" present, we call:
+
+  (assess-with-filesystem '(\"foo\")
+    (code-here)
+    (and-some-more-forms))
+
+You should *not* depend on where exactly the hierarchy is created.
+By default, a new directory in `temporary-file-directory' is
+created and the specification is evaluated there, but this is up
+for change."
+  (declare (indent 1))
+  (let ((temp-root (make-symbol "temp-root"))
+        (old-dd (make-symbol "old-dd")))
+    `(let ((,temp-root (make-temp-file "temp-fs-" t))
+           (,old-dd default-directory))
+       (unwind-protect
+           (progn
+             (setq default-directory ,temp-root)
+             (mapc (lambda (s) (assess-with-filesystem--init s ".")) ,spec)
+             ,@forms)
+         (delete-directory ,temp-root t)
+         (setq default-directory ,old-dd)))))
+;; #+END_SRC
+;; ** Indentation functions
+
+;; There are two main ways to test indentation -- we can either take unindented
+;; text, indent it, and then compare it to something else; or, we can roundtrip
+;; -- take indented code, unindent it, re-indent it again and see whether we 
end
+;; up with what we started. Assess supports both of these.
+
+;; Additionally, there are two different ways to specific a mode -- we can 
either
+;; define it explicitly or, if we are opening from a file, we can use the 
normal
+;; `auto-mode-alist' functionality to determine the mode. Assess supports both
+;; of these also.
+
+;; The simplest function is `assess-indentation=' which we can use as follows.
+;; In this case, we have mixed a multi-line string and a single line with
+;; control-n characters; this is partly to show that we can, and partly to make
+;; sure that the code works both in an `org-mode' buffer and an ~*Org Src*~ 
buffer.
+
+;; #+begin_src elisp
+;;   (assess-indentation=
+;;    'emacs-lisp-mode
+;;    "(assess-with-find-file
+;;   \"~/.emacs\"
+;;   (buffer-string))"
+;;    "(assess-with-find-file\n    \"~/.emacs\"\n  (buffer-string))")
+;; #+end_src
+
+;; #+RESULTS:
+;; : t
+
+;; Probably more useful is `assess-roundtrip-indentation=' which allows us to
+;; just specify the indented form; in this case, the string is first unindented
+;; (every line starts at the first position) and then reindented. This saves 
the
+;; effort of keeping the text in both the indented and unindent forms in sync
+;; (but without the indentation).
+
+;; #+begin_src elisp
+;;   (assess-roundtrip-indentation=
+;;    'emacs-lisp-mode
+;;    "(assess-with-find-file\n    \"~/.emacs\"\n  (buffer-string))")
+;; #+end_src
+
+;; #+RESULTS:
+;; : t
+
+;; While these are useful for simple forms of indentation checking, they have
+;; the significant problem of writing indented code inside an Emacs string. An
+;; easier solution for longer pieces of code is to use
+;; `assess-file-roundtrip-indentation='. This opens a file (safely using
+;; `assess-make-related-file'), unindents, and reindents. The mode must be set
+;; up automatically by the file type.
+
+;; #+begin_src elisp
+;;   (assess-file-roundtrip-indentation=
+;;     "assess.el")
+;; #+end_src
+
+;; #+RESULTS:
+
+;; All of these methods are fully supported with ert explainer functions -- as
+;; before they use diff where possible to compare the two forms.
+
+
+;; *** Implementation
+
+;; We start with some functionality for making Emacs quiet while indenting,
+;; otherwise we will get a large amount of spam on the command line. Emacs 
needs
+;; to have a better technique for shutting up `message'.
+
+;; #+begin_src emacs-lisp
+(defun assess--indent-buffer (&optional column)
+  (cond
+   (column
+    (indent-region (point-min) (point-max) column))
+   ;; if indent-region-function is set, use it, and hope that it is not
+   ;; noisy.
+   (indent-region-function
+    (funcall indent-region-function (point-min) (point-max)))
+   (t
+    (seq-map
+     (lambda (m)
+       (goto-char m)
+       (indent-according-to-mode))
+     (m-buffer-match-line-start (current-buffer))))))
+
+(defun assess--indent-in-mode (mode unindented)
+  (with-temp-buffer
+    (insert
+     (assess-to-string unindented))
+    (funcall mode)
+    (assess--indent-buffer)
+    (buffer-string)))
+;; #+end_src
+
+;; Now for the basic indentation= comparison.
+
+;; #+begin_src emacs-lisp
+(defun assess-indentation= (mode unindented indented)
+  "Return non-nil if UNINDENTED indents in MODE to INDENTED.
+Both UNINDENTED and INDENTED can be any value usable by
+`assess-to-string'. Indentation is performed using
+`indent-region', which MODE should set up appropriately.
+
+See also `assess-file-roundtrip-indentation=' for an
+alternative mechanism."
+  (assess=
+   (assess--indent-in-mode
+    mode
+    unindented)
+   indented))
+
+(defun assess-explain-indentation= (mode unindented indented)
+  "Explanation function for `assess-indentation='."
+  (assess-explain=
+   (assess--indent-in-mode
+    mode
+    unindented)
+   indented))
+
+(put 'assess-indentation= 'ert-explainer 'assess-explain-indentation=)
+;; #+end_src
+
+;; Roundtripping.
+
+;; #+begin_src emacs-lisp
+(defun assess--buffer-unindent (buffer)
+  (with-current-buffer
+      buffer
+    (assess--indent-buffer 0)))
+
+(defun assess--roundtrip-1 (comp mode indented)
+  (with-temp-buffer
+    (funcall comp
+             mode
+             (progn
+               (insert
+                (assess-to-string indented))
+               (assess--buffer-unindent (current-buffer))
+               (buffer-string))
+             indented)))
+
+(defun assess-roundtrip-indentation= (mode indented)
+  "Return t if in MODE, text in INDENTED is corrected indented.
+
+This is checked by unindenting the text, then reindenting it according
+to MODE.
+
+See also `assess-indentation=' and
+`assess-file-roundtrip-indentation=' for alternative
+mechanisms of checking indentation."
+  (assess--roundtrip-1
+   #'assess-indentation=
+   mode indented))
+
+(defun assess-explain-roundtrip-indentation= (mode indented)
+  "Explanation function for `assess-roundtrip-indentation='."
+  (assess--roundtrip-1
+   #'assess-explain-indentation=
+   mode indented))
+
+(put 'assess-roundtrip-indentation=
+     'ert-explainer
+     'assess-explain-roundtrip-indentation=)
+;; #+end_src
+
+;; And file based checking.
+
+;; #+begin_src emacs-lisp
+(defun assess--file-roundtrip-1 (comp file)
+  (funcall
+   comp
+   (assess-with-find-file
+       (assess-make-related-file file)
+     (assess--buffer-unindent (current-buffer))
+     (assess--indent-buffer)
+     (buffer-string))
+   file))
+
+(defun assess-file-roundtrip-indentation= (file)
+  "Return t if text in FILE is indented correctly.
+
+FILE is copied with `assess-make-related-file', so this
+function should be side-effect free whether or not FILE is
+already open. The file is opened with `find-file-noselect', so
+hooks associated with interactive visiting of a file should all
+be called, with the exception of directory local variables, as
+the copy of FILE will be in a different directory."
+  (assess--file-roundtrip-1
+   #'assess= file))
+
+(defun assess-explain-file-roundtrip-indentation= (file)
+  "Explanation function for `assess-file-roundtrip-indentation=."
+  (assess--file-roundtrip-1
+   #'assess-explain= file))
+
+(put 'assess-file-roundtrip-indentation=
+     'ert-explainer
+     'assess-explain-file-roundtrip-indentation=)
+;; #+end_src
+
+;; ** Font-Lock
+
+;; Here we define two predicates that can be used to checking
+;; fontification/syntax highlighting; as with indentation, one accepts strings
+;; but requires an explicit mode, while the other reads from file and depends 
on
+;; the normal Emacs mechanisms for defining the mode. These two are
+;; `assess-font-at=' and `assess-file-font-at='. Both of these have the same
+;; interface and have attached explainer functions. Here, we show examples with
+;; `assess-face-at='.
+
+;; The simplest use is to specify a point location and a face. This returns 
true
+;; if at least that face is present at the location.
+
+;; #+begin_src elisp
+;;    (assess-face-at=
+;;     "(defun x ())"
+;;     'emacs-lisp-mode
+;;     2
+;;     'font-lock-keyword-face)
+;; #+end_src
+
+;; It is also possible to specify several locations in a list, with a single
+;; face. This checks that the given font is present at every location.
+
+;; #+begin_src elisp
+;;    (assess-face-at=
+;;     "(defun x ())
+;; (defun y ())
+;; (defun z ())"
+;;     'emacs-lisp-mode
+;;     '(2 15 28)
+;;     'font-lock-keyword-face)
+;; #+end_src
+
+;; Or, we can specify a list of faces in which case the locations and faces are
+;; checked in a pairwise manner.
+
+;; #+begin_src elisp
+;;    (assess-face-at=
+;;     "(defun x ())"
+;;     'emacs-lisp-mode
+;;     '(2 8)
+;;     '(font-lock-keyword-face font-lock-function-name-face))
+;; #+end_src
+
+;; It is also possible to define locations with regexps; again either one or
+;; multiple regexps can be used. With a single string, all matches are checked,
+;; with the first match to the first is checked, then the next match to the
+;; second, incrementally.
+
+;; #+begin_src elisp
+;;    (assess-face-at=
+;;     "(defun x ())\n(defun y ())\n(defun z ())"
+;;     'emacs-lisp-mode
+;;     "defun"
+;;     'font-lock-keyword-face)
+
+;;    (assess-face-at=
+;;     "(defun x ())\n(defmacro y ())\n(defun z ())"
+;;     'emacs-lisp-mode
+;;     '("defun" "defmacro" "defun")
+;;     'font-lock-keyword-face)
+;; #+end_src
+
+
+;; The locations can also be specified as a `lambda' which takes a single
+;; argument of a buffer. The return result can be any form of location accepted
+;; by `assess-face-at=', including a list of match data generated, as in this
+;; case, by the `m-buffer' package.
+
+;; #+begin_src elisp
+;;    (assess-face-at=
+;;     "(defun x ())\n(defun y ())\n(defun z ())"
+;;     'emacs-lisp-mode
+;;     (lambda(buf)
+;;       (m-buffer-match buf "defun"))
+;;     'font-lock-keyword-face)
+;; #+end_src
+
+
+;; *** Implementation
+
+;; First, `assess-face-at='.
+
+
+;; #+begin_src emacs-lisp
+(defun assess--face-at-location=
+    (location face property throw-on-nil)
+  ;; it's match data
+  (if (listp location)
+      ;; We need to test every point but not the last because the match is
+      ;; passed the end.
+      (let ((all nil))
+        (cl-loop for i from
+                 (marker-position (car location))
+                 below
+                 (marker-position (cadr location))
+                 do
+                 (setq all
+                       (cons (assess--face-at-location=
+                              i face
+                              property throw-on-nil)
+                             all)))
+        (seq-every-p #'identity all))
+    (let* ((local-faces
+            (get-text-property location property))
+           (rtn
+            ;; for face this can be one of -- a face name (a symbol or string)
+            ;; a list of faces, or a plist of face attributes
+            (pcase local-faces
+              ;; compare directly
+              ((pred symbolp)
+               (eq face local-faces))
+              ;; give up -- we should probably be able to compare the plists 
here.
+              ((and `(,s . ,_)
+                    (guard (keywordp s)))
+               nil)
+              ;; compare that we have at least this.
+              ((and `(,s . ,_)
+                    (guard (symbolp s)))
+               (member face s)))))
+      (if (and throw-on-nil
+               (not rtn))
+          (throw
+           'face-non-match
+           (format "Face does not match expected value
+\tExpected: %s
+\tActual: %s
+\tLocation: %s
+\tLine Context: %s
+\tbol Position: %s
+"
+                   face local-faces location
+                   (thing-at-point 'line)
+                   (m-buffer-at-line-beginning-position
+                    (current-buffer) location)))
+        rtn))))
+
+
+(defun assess--face-at=
+    (buffer locations faces property throw-on-nil)
+  (let* (
+         ;; default property
+         (property (or property 'face))
+         ;; make sure we have a list of locations
+         (locations
+          (pcase locations
+            ((pred functionp)
+             (funcall locations buffer))
+            ((pred listp)
+             locations)
+            (_ (list locations))))
+         (first-location
+          (car locations))
+         ;; make sure we have a list of markers
+         (locations
+          (cond
+           ((integerp first-location)
+            (m-buffer-pos-to-marker buffer locations))
+           ((stringp first-location)
+            (m-buffer-match-multi locations :buffer buffer))
+           ;; markers
+           ((markerp first-location)
+            locations)
+           ;; match data
+           ((and (listp first-location)
+                 (markerp (car first-location)))
+            locations)))
+          ;; make sure we have a list of faces
+          (faces
+           (if (and (listp faces)
+                    ;; but not nil
+                    (not (eq nil faces)))
+               faces
+             (list faces)))
+          ;; make sure faces is as long as locations
+          (faces
+           (progn
+             (while (> (length locations)
+                       (length faces))
+               ;; cycle faces if needed
+               (setq faces (append faces (seq-copy faces))))
+             faces)))
+    (seq-every-p
+     (lambda (it)
+       (assess--face-at-location=
+        (car it) (cdr it) property throw-on-nil))
+     (seq-mapn #'cons locations faces))))
+
+(defun assess--face-at=-1 (x mode locations faces property throw-on-nil)
+  (with-temp-buffer
+    (insert (assess-to-string x))
+    (funcall mode)
+    (font-lock-fontify-buffer)
+    (assess--face-at= (current-buffer) locations faces property throw-on-nil)))
+
+(defun assess-face-at=
+    (x mode locations faces &optional property)
+  "Return non-nil if in X with MODE at MARKERS, FACES are present on PROPERTY.
+
+This function tests if one or more faces are present at specific
+locations in some text. It operates over single or multiple
+values for both locations and faces; if there are more locations
+than faces, then faces will be cycled over. If locations are
+match data, then each the beginning and end of each match are
+tested against each face.
+
+X can be a buffer, file name or string -- see
+`assess-to-string' for details.
+
+MODE is the major mode with which to fontify X -- actually, it
+will just be a function called to initialize the buffer.
+
+LOCATIONS can be either one or a list of the following things:
+integer positions in X; markers in X (or nil!); match data in X;
+or strings which match X. If this is a list, all items in list
+should be of the same type.
+
+FACES can be one or more faces.
+
+PROPERTY is the text property on which to check the faces.
+
+See also `assess-to-string' for treatment of the parameter X.
+
+See `assess-file-face-at=' for a similar function which
+operates over files and takes the mode from that file."
+  (assess--face-at=-1 x mode locations faces property nil))
+
+(defun assess-explain-face-at=
+    (x mode locations faces &optional property)
+  (catch 'face-non-match
+    (assess--face-at=-1 x mode locations faces property t)))
+
+(put 'assess-face-at=
+     'ert-explainer
+     'assess-explain-face-at=)
+;; #+end_src
+
+;; Followed by `assess-file-face-at='.
+
+;; #+begin_src emacs-lisp
+(defun assess--file-face-at=-1 (file locations faces property throw-on-nil)
+  (assess-with-find-file
+      (assess-make-related-file file)
+    (font-lock-fontify-buffer)
+    (assess--face-at= (current-buffer) locations faces property throw-on-nil)))
+
+(defun assess-file-face-at= (file locations faces &optional property)
+  (assess--file-face-at=-1 file locations faces property nil))
+
+(defun assess-explain-file-face-at= (file locations faces &optional property)
+  (catch 'face-non-match
+    (assess--file-face-at=-1 file locations faces property t)))
+
+(put 'assess-file-face-at=
+     'ert-explainer
+     'assess-explain-file-face-at=)
+;; #+end_src
+
+
+;; #+begin_src emacs-lisp
+(defmacro assess-with-safe-user-directory (&rest body)
+  (declare (debug t))
+  `(let ((user-emacs-directory (make-temp-file "emacs-assess" t)))
+     ,@body))
+;; #+end_src
+
+
+;; #+begin_src emacs-lisp
+(provide 'assess)
+;;; assess.el ends here
+;; #+end_src
diff --git a/lisp/emacs-lisp/m-buffer/m-buffer-at.el 
b/lisp/emacs-lisp/m-buffer/m-buffer-at.el
new file mode 100644
index 0000000..c879971
--- /dev/null
+++ b/lisp/emacs-lisp/m-buffer/m-buffer-at.el
@@ -0,0 +1,89 @@
+;;; m-buffer-at.el --- Stateless point functions -*- lexical-binding: t -*-
+
+;;; Header:
+
+;; This file is not part of Emacs
+
+;; The contents of this file are subject to the GPL License, Version 3.0.
+
+;; Copyright (C) 2014, Phillip Lord, Newcastle University
+
+;; This program is free software: you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation, either version 3 of the License, or
+;; (at your option) any later version.
+
+;; This program is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;; GNU General Public License for more details.
+
+;; You should have received a copy of the GNU General Public License
+;; along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+;;; Commentary:
+
+;; Provides stateless equivalents to many core Emacs functions, that provide
+;; information about a buffer. Most of these functions take either a buffer as
+;; a parameter or a location, which is either a marker (with a non-nil buffer
+;; and location) or a buffer and integer.
+
+;; These functions are generally competitive with the originals in terms of
+;; speed.
+
+;;; Status:
+
+;; There are lots more to do, but the interface should be stable.
+
+;;; Code:
+
+;; #+begin_src emacs-lisp
+
+(require 'm-buffer-macro)
+
+(defun m-buffer-at-point (buffer)
+  "Return the location of point in BUFFER.
+See also `point'."
+  (with-current-buffer
+      buffer
+    (point)))
+
+(defun m-buffer-at-eolp (&rest location)
+  "Return t if LOCATION is at the end of a line.
+See also `eolp'."
+  (m-buffer-with-current-location
+      location
+    (eolp)))
+
+(defun m-buffer-at-bolp (&rest location)
+  "Return t if LOCATION is at the begining of a line.
+See also `bolp'"
+  (m-buffer-with-current-location
+      location
+    (bolp)))
+
+(defun m-buffer-at-line-beginning-position (&rest location)
+  "Return the start of the line of LOCATION."
+  (m-buffer-with-current-location
+      location
+    (line-beginning-position)))
+
+(defun m-buffer-at-line-end-position (&rest location)
+  "Return the end of the line of LOCATION."
+  (m-buffer-with-current-location
+      location
+    (line-end-position)))
+
+(defun m-buffer-at-narrowed-p (buffer)
+  (with-current-buffer
+      buffer
+    (buffer-narrowed-p)))
+
+(defun m-buffer-at-string (buffer)
+  (with-current-buffer
+      buffer
+    (buffer-string)))
+
+(provide 'm-buffer-at)
+;;; m-buffer-at.el ends here
+;; #+end_src
diff --git a/lisp/emacs-lisp/m-buffer/m-buffer-macro.el 
b/lisp/emacs-lisp/m-buffer/m-buffer-macro.el
new file mode 100644
index 0000000..d716ee5
--- /dev/null
+++ b/lisp/emacs-lisp/m-buffer/m-buffer-macro.el
@@ -0,0 +1,123 @@
+;;; m-buffer-macro.el --- Create and dispose of markers -*- lexical-binding: t 
-*-
+
+;;; Header:
+
+;; This file is not part of Emacs
+
+;; The contents of this file are subject to the GPL License, Version 3.0.
+
+;; Copyright (C) 2014, Phillip Lord, Newcastle University
+
+;; This program is free software: you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation, either version 3 of the License, or
+;; (at your option) any later version.
+
+;; This program is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;; GNU General Public License for more details.
+
+;; You should have received a copy of the GNU General Public License
+;; along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+;;; Commentary:
+
+;; This file provides some utility macros which help to support stateless
+;; operation on buffers, by restoring global state after to what it was before
+;; the macro starts.
+
+;; These macros are quite useful, but with the exception of
+;; `m-buffer-with-markers', they are mostly meant to underpin `m-buffer-at'. 
The
+;; aim is that all the cases where one of these macros is used with a single 
form
+;; from core Emacs should be provided by m-buffer-at (although this is not the
+;; case yet). These macros might be more efficient if there are a lot of calls 
to
+;; group together.
+
+;;; Code:
+
+;; ** Markers
+
+;; Markers are generally much nicer than integers, but needs cleaning up
+;; afterwards if a lot are created. It's possible to do this using
+;; `m-buffer-nil-marker', but it can be a bit painful. This form looks like a
+;; `let' form, but removes markers at the end.
+
+;; #+begin_src emacs-lisp
+(defmacro m-buffer-with-markers (varlist &rest body)
+  "Bind variables after VARLIST then eval BODY.
+VARLIST is of the same form as `let'. All variables should
+contain markers or collections of markers. All markers are niled
+after BODY."
+  ;; indent let part specially, and debug like let
+  (declare (indent 1)(debug let))
+  ;; so, create a rtn var with make-symbol (for hygene)
+  (let* ((rtn-var (make-symbol "rtn-var"))
+         (marker-vars
+          (mapcar 'car varlist))
+         (full-varlist
+          (append
+           varlist
+           `((,rtn-var
+              (progn
+                ,@body))))))
+    `(let* ,full-varlist
+       (m-buffer-nil-marker
+        (list ,@marker-vars))
+       ,rtn-var)))
+;; #+end_src
+
+;; ** Point and Buffer
+
+;; These macros are extensions of `with-current-buffer', and `save-excursion',
+;; which set the current buffer and location.
+
+;; #+begin_src emacs-lisp
+(defmacro m-buffer-with-current-marker
+    (marker &rest body)
+  "At MARKER location run BODY."
+  (declare (indent 1) (debug t))
+  `(with-current-buffer
+       (marker-buffer ,marker)
+     (save-excursion
+       (goto-char ,marker)
+       ,@body)))
+
+(defmacro m-buffer-with-current-position
+    (buffer location &rest body)
+  "In BUFFER at LOCATION, run BODY."
+  (declare (indent 2)
+           (debug t))
+  `(with-current-buffer
+       ,buffer
+     (save-excursion
+       (goto-char ,location)
+      ,@body)))
+;; #+end_src
+
+;; Combines the last two!
+
+;; #+begin_src emacs-lisp
+(defmacro m-buffer-with-current-location
+    (location &rest body)
+  "At LOCATION, run BODY.
+LOCATION should be a list. If a one element list, it is a marker.
+If a two element, it is a buffer and position."
+  (declare (indent 1) (debug t))
+  ;; multiple eval of location!
+  (let ((loc (make-symbol "loc")))
+    `(let ((,loc ,location))
+       (if (= 1 (length ,loc))
+           (m-buffer-with-current-marker
+               (nth 0 ,loc)
+             ,@body)
+         (if (= 2 (length ,loc))
+             (m-buffer-with-current-position
+                 (nth 0 ,loc)
+                 (nth 1 ,loc)
+               ,@body)
+           (error "m-buffer-with-current-location requires a list of one or 
two elements"))))))
+
+(provide 'm-buffer-macro)
+;;; m-buffer-macro.el ends here
+;; #+end_src
diff --git a/lisp/emacs-lisp/m-buffer/m-buffer-pkg.el 
b/lisp/emacs-lisp/m-buffer/m-buffer-pkg.el
new file mode 100644
index 0000000..07ff27e
--- /dev/null
+++ b/lisp/emacs-lisp/m-buffer/m-buffer-pkg.el
@@ -0,0 +1,2 @@
+(define-package "m-buffer" "0.4" "Buffer Manipulation Functions"
+  '((emacs "24.3")))
diff --git a/lisp/emacs-lisp/m-buffer/m-buffer.el 
b/lisp/emacs-lisp/m-buffer/m-buffer.el
new file mode 100644
index 0000000..c3f3523
--- /dev/null
+++ b/lisp/emacs-lisp/m-buffer/m-buffer.el
@@ -0,0 +1,984 @@
+;;; m-buffer.el --- List-Oriented, Functional Buffer Manipulation -*- 
lexical-binding: t -*-
+
+;;; Header:
+
+;; This file is not part of Emacs
+
+;; Author: Phillip Lord <address@hidden>
+;; Maintainer: Phillip Lord <address@hidden>
+;; Version: 0.15
+;; Package-Requires: ((seq "2.14"))
+
+;; The contents of this file are subject to the GPL License, Version 3.0.
+
+;; Copyright (C) 2014, 2015, 2016, 2017 Phillip Lord
+
+;; This program is free software: you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation, either version 3 of the License, or
+;; (at your option) any later version
+
+;; This program is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;; GNU General Public License for more details.
+
+;; You should have received a copy of the GNU General Public License
+;; along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+;;; Commentary:
+
+;; This file provides a set of list-oriented functions for operating over the
+;; contents of buffers, mostly revolving around regexp searching, and regions.
+;; They avoid the use of looping, manipulating global state with `match-data'.
+;; Many high-level functions exist for matching sentences, lines and so on.
+
+;; Functions are generally purish: i.e. that is those functions which do
+;; change state, by for example replacing text or adding overlays, should only
+;; change state in one way; they will not affect point, current buffer, match
+;; data or so forth.
+
+;; Likewise to protect against changes in state, markers are used rather than
+;; integer positions. This means that it is possible, for example, to search
+;; for regexp matches and then replace them all without the earlier
+;; replacements invalidating the location of the later ones. Otherwise
+;; replacements need to be made in reverse order. This can have implications
+;; for performance, so m-buffer also provides functions for making markers nil;
+;; there are also macros which help manage markers in `m-buffer-macro'.
+
+;; Where possible, functions share interfaces. So most of the match functions
+;; take a list of "match" arguments, either position or as a plist, which 
avoids
+;; using lots of `nil' arguments. Functions operating on matches take a list of
+;; `match-data' as returned by the match functions, making it easy to chain
+;; matches.
+
+;; This file is documented using lentic.el. Use
+;; [[http://github.com/phillord/lentic-server][lentic-server]] to view.
+
+;;; Status:
+
+;; m-buffer.el is now stable and is expected to change only in
+;; forward-compatible ways.
+
+;;; Code:
+
+;; #+begin_src emacs-lisp
+(require 'seq)
+(require 'm-buffer-macro)
+
+;; #+end_src
+
+;; ** Regexp Matching
+
+;; We first provide a single match function, `m-bufffer-match' which converts
+;; between Emacs' stateful matching and a more sequence-oriented interface.
+
+;; This function also defines the "match" arguments which are a standard set of
+;; arguments used throughout this package.
+
+;; #+begin_src emacs-lisp
+(defun m-buffer-match (&rest match)
+  "Return a list of all `match-data' for MATCH.
+MATCH may be of the forms:
+BUFFER REGEXP &optional MATCH-OPTIONS
+WINDOW REGEXP &optional MATCH-OPTIONS
+MATCH-OPTIONS
+
+If BUFFER is given, search this buffer. If WINDOW is given search
+the visible window. MATCH-OPTIONS is a plist with any of the
+following keys:
+:buffer -- the buffer to search
+:regexp -- the regexp to search with
+:begin -- the start of the region to search -- default point min
+:end -- the end of the region to search -- default point max
+:post-match -- function called after a match -- default nil
+:widen -- if true, widen buffer first -- default nil
+:case-fold-search value of `case-fold-search' during search.
+If :default accept the current buffer-local value
+:numeric -- if true, return integers not markers
+
+If options are expressed in two places, the plist form takes
+precedence over positional args. So calling with both a first
+position buffer and a :buffer arg will use the second. Likewise,
+if a window is given as first arg and :end is given, then
+the :end value will be used.
+
+REGEXP should advance point (i.e. not be zero-width) or the
+function will loop infinitely. POST-MATCH can be used to avoid
+this. The buffer is searched forward."
+  (apply 'm-buffer--match-1
+         (m-buffer--normalize-args match)))
+;; #+end_src
+
+;; The match function is actually implemented here in the `m-buffer--match-1'
+;; function, with positional arguments.
+
+;; #+begin_src emacs-lisp
+(defun m-buffer--match-1 (buffer regexp begin end
+                                post-match widen cfs
+                                numeric)
+  "Return a list of `match-data'.
+
+This is an internal function: please prefer `m-buffer-match'.
+
+BUFFER -- the buffer.
+REGEXP -- the regexp.
+BEGIN -- the start of the region to search
+END -- the end of the region to search
+POST-MATCH -- function to run after each match
+POST-MATCH is useful for zero-width matches which will otherwise
+cause infinite loop. The buffer is searched forward. POST-MATCH
+return can also be used to terminate the matching by returning nil.
+WIDEN -- call widen first.
+CFS -- Non-nil if searches and matches should ignore case.
+NUMERIC -- Non-nil if we should return integers not markers."
+;; #+end_src
+
+;; We start by saving everything to ensure that we do not pollute the global
+;; state. This means match-data, point, narrowing and current buffer! Hopefully
+;; this is all the global state that exists and that we are changing.
+
+;; #+begin_src emacs-lisp
+  (with-current-buffer
+      buffer
+    (save-match-data
+      (save-excursion
+        (save-restriction
+          (when widen (widen))
+;; #+end_src
+
+;; This let form is doing a number of things. It sets up a dynamic binding for
+;; `case-fold-search' (which works even though we are using lexical binding),
+;; ensures a non-nil value for =end-bound= and defines a sentinal value that
+;; =post-match-return= can use to end early.
+
+;; #+begin_src emacs-lisp
+          (let ((rtn nil)
+                (post-match-return t)
+                (end-bound (or end (point-max)))
+                ;; over-ride default if necessary
+                (case-fold-search
+                 (if (eq :default cfs)
+                     case-fold-search
+                   cfs)))
+;; #+end_src
+
+;; We start at the beginning. There was no particularly good reason for this, 
and
+;; it would have made just as much sense to go backward.
+
+;; #+begin_src emacs-lisp
+            (goto-char
+             (or begin
+                 (point-min)))
+            (while
+                (and
+;; #+end_src
+
+;; The original purpose for =post-match-return= was for zero-width matches --
+;; these do not advance point beyond their end, so the while loop never
+;; terminates. Unfortunately, avoiding this depends on the regexp being called,
+;; so we provide the most general solution of all.
+
+;; As well as this, we check the return value of =post-match-return=, so as 
well
+;; as advancing `point' by side-effect, we can also use it to terminate the 
look
+;; at any point that we want; for example, we can terminate after the first 
match
+;; which feels more efficient than searching the whole buffer then taking the
+;; first match.
+
+;; #+begin_src emacs-lisp
+                 post-match-return
+                 ;; we need to check we are less than the end-bound
+                 ;; or re-search-forward will break
+                 (<= (point) end-bound)
+                 (re-search-forward
+                  regexp end-bound
+                  t))
+;; #+end_src
+
+;; Store the `match-data' in a backward list, run post-match. Finally, reverse
+;; and terminate.
+
+;; #+begin_src emacs-lisp
+              (setq rtn
+                    (cons
+                     (if numeric
+                         (m-buffer-marker-to-pos-nil
+                          (match-data))
+                       (match-data))
+                     rtn))
+              (when post-match
+                (setq post-match-return (funcall post-match))))
+            (reverse rtn)))))))
+;; #+end_src
+
+;; This method implements the argument list processing. I find this interface
+;; fairly attractive to use since it takes the two "main" arguments -- buffer 
and
+;; regexp -- as positional args optionally, and everything else as keywords. 
The
+;; use of keywords is pretty much essential as have eight arguments most of 
which
+;; are not essential.
+
+;; This is fairly close to the logic provided by `cl-defun' which I wasn't 
aware
+;; of when I wrote this. However `cl-defun' does not allow optional arguments
+;; before keyword arguments -- all the optional arguments have to be given if 
we
+;; are to use keywords.
+
+;; #+begin_src emacs-lisp
+(defun m-buffer--normalize-args (match-with)
+  "Manipulate args into a standard form and return as a list.
+MATCH-WITH are these args. This is an internal function."
+  (let* (
+         ;; split up into keyword and non keyword limits
+         (args
+          (seq-take-while
+           (lambda (x) (not (keywordp x)))
+           match-with))
+         (pargs
+          (seq-drop-while
+           (lambda (x) (not (keywordp x)))
+           match-with))
+         ;; sort actual actual parameters
+         (first (car args))
+         ;; buffer may be first
+         (buffer
+          (or (plist-get pargs :buffer)
+              (and (bufferp first) first)))
+         ;; or window may be first
+         (window
+          (or (plist-get pargs :window)
+              (and (windowp first) first)))
+         ;; regexp always comes second
+         (regexp
+          (or (plist-get pargs :regexp)
+              (nth 1 args)))
+         ;; begin depends on other arguments
+         (begin
+          (or (plist-get pargs :begin)
+              (and window (window-start window))))
+         ;; end depends on other arguments
+         (end
+          (or (plist-get pargs :end)
+              (and window (window-end window))))
+         ;; pm
+         (post-match
+          (plist-get pargs :post-match))
+
+         ;; widen
+         (widen
+           (plist-get pargs :widen))
+
+         ;; case-fold-search this needs to overwrite the buffer contents iff
+         ;; set, otherwise be ignored, so we need to distinguish a missing
+         ;; property and a nil one
+         (cfs
+          (if (plist-member pargs :case-fold-search)
+              (plist-get pargs :case-fold-search)
+            :default))
+
+         ;; numeric
+         (numeric
+          (plist-get pargs :numeric)))
+
+    (list buffer regexp begin end post-match widen cfs numeric)))
+;; #+end_src
+
+;; Finally, this function provides a link between the match function, and the
+;; match manipulation functions. We can either choose to match once against a 
set
+;; of arguments and then apply multiple manipulations on the returned match 
data.
+;; Or just use the match manipulation function directly.
+
+;; The first version of `m-buffer' did not include this but it required lots of
+;; nested calls which seem inconvenient.
+
+;; #+begin_example
+;; (m-buffer-match-manipulate
+;;   (m-buffer-match (current-buffer) "hello"))
+;; #+end_example
+
+;; I think that convienience is worth the overhead.
+
+;; #+begin_src emacs-lisp
+(defun m-buffer-ensure-match (&rest match)
+  "Ensure that we have MATCH data.
+If a single arg, assume it is match data and return. If multiple
+args, assume they are of the form accepted by
+`m-buffer-match'."
+  (cond
+   ;; we have match data
+   ((= 1 (length match))
+    (car match))
+   ((< 1 (length match))
+    (apply 'm-buffer-match match))
+   (t
+    (error "Invalid arguments"))))
+;; #+end_src
+
+;; ** Match Data Manipulation Functions
+
+;; These functions manipulate lists of either match-data or match arguments in
+;; some way.
+
+;; #+begin_src emacs-lisp
+(defun m-buffer-buffer-for-match (match-data)
+  "Given some MATCH-DATA return the buffer for that data."
+  (marker-buffer (caar match-data)))
+
+(defun m-buffer-match-nth-group (n match-data)
+  "Fetch the Nth group from MATCH-DATA."
+  (seq-map
+   (lambda (m)
+     (let ((drp
+            (seq-drop m (* 2 n))))
+       (list
+        (car drp) (cadr drp))))
+   match-data))
+
+(defun m-buffer-match-begin-n (n &rest match)
+  "Return markers to the start of the Nth group in MATCH.
+MATCH may be of any form accepted by `m-buffer-ensure-match'. Use
+`m-buffer-nil-marker' after the markers have been finished with
+or they will slow future use of the buffer until garbage collected."
+  (seq-map
+   (lambda (m)
+     (nth
+      (* 2 n) m))
+   (apply 'm-buffer-ensure-match match)))
+
+(defun m-buffer-match-begin-n-pos (n &rest match)
+  "Return positions of the start of the Nth group in MATCH.
+MATCH may be of any form accepted by `m-buffer-ensure-match'. If
+`match-data' is passed markers will be set to nil after this
+function. See `m-buffer-nil-marker' for details."
+  (m-buffer-marker-to-pos-nil
+   (apply 'm-buffer-match-begin-n
+          n match)))
+
+(defun m-buffer-match-begin (&rest match)
+  "Return a list of markers to the start of MATCH.
+MATCH may of any form accepted by `m-buffer-ensure-match'. Use
+`m-buffer-nil-marker' after the markers have been used or they
+will slow future changes to the buffer."
+  (apply 'm-buffer-match-begin-n 0 match))
+
+(defun m-buffer-match-begin-pos (&rest match)
+  "Return a list of positions at the start of matcher.
+MATCH may be of any form accepted by `m-buffer-ensure-match'.
+If `match-data' is passed markers will be set to nil after this
+function. See `m-buffer-nil-marker' for details."
+  (apply 'm-buffer-match-begin-n-pos 0 match))
+
+(defun m-buffer-match-end-n (n &rest match)
+  "Return markers to the end of the match to the Nth group.
+MATCH may be of any form accepted by `m-buffer-ensure-match'.
+If `match-data' is passed markers will be set to nil after this
+function. See `m-buffer-nil-marker' for details."
+  (seq-map
+   (lambda (m)
+     (nth
+      (+ 1 (* 2 n))
+      m))
+   (apply 'm-buffer-ensure-match match)))
+
+(defun m-buffer-match-end-n-pos (n &rest match)
+  "Return positions of the end Nth group of MATCH.
+MATCH may be of any form accepted by `m-buffer-ensure-match'.
+If `match-data' is passed markers will be set to nil after this
+function. See `m-buffer-nil-marker' for details."
+  (m-buffer-marker-to-pos-nil
+   (apply 'm-buffer-match-end-n-pos
+          n match)))
+
+(defun m-buffer-match-end (&rest match)
+  "Return a list of markers to the end of MATCH to regexp in buffer.
+MATCH may be of any form accepted by `m-buffer-ensure-match'. Use
+`m-buffer-nil-marker' after the markers have been used or they
+will slow future changes to the buffer."
+  (apply 'm-buffer-match-end-n 0 match))
+
+(defun m-buffer-match-end-pos (&rest match)
+  "Return a list of positions to the end of the match.
+MATCH may be of any form accepted by `m-buffer-ensure-match'.
+If `match-data' is passed markers will be set to nil after this
+function. See `m-buffer-nil-marker' for details."
+  (m-buffer-marker-to-pos-nil
+   (apply 'm-buffer-match-end match)))
+;; #+end_src
+
+;; ** Match Utility and Predicates
+
+;; *** Subtraction
+
+;; Some predicates and the ability to subtract to lists of matches from each
+;; other. This makes up for limitations in Emacs regexp which can't do "match x
+;; but not y".
+
+;; #+begin_src emacs-lisp
+(defun m-buffer-match-equal (m n)
+  "Return true if M and N are cover the same region.
+Matches are equal if they match the same region; subgroups are
+ignored."
+  (and
+   (equal
+    (car m)
+    (car n))
+   (equal
+    (cadr m)
+    (cadr n))))
+;; #+end_src
+
+;; A nice simple implementation for the general purpose solution.
+;; Unfortunately, performance sucks, running in quadratic time.
+
+;; #+begin_src emacs-lisp
+(defun m-buffer-match-subtract (m n)
+  "Remove from M any match in N.
+Matches are equivalent if overall they match the same
+area; subgroups are ignored.
+See also `m-buffer-match-exact-subtract' which often
+runs faster but has some restrictions."
+  (seq-remove
+   (lambda (o)
+     (seq-some
+      (lambda (p)
+        (m-buffer-match-equal o p))
+      n))
+   m))
+;; #+end_src
+
+;; The ugly and complicated and less general solution. But it runs in linear
+;; time.
+
+;; #+begin_src emacs-lisp
+(defun m-buffer-match-exact-subtract (m n)
+  "Remove from M any match in N.
+Both M and N must be fully ordered, and any element in N must be
+in M."
+  (if n
+      ;; n-eaten contains the remaining elements of n that we haven't tested
+      ;; for yet. We throw them away as we go
+      (let ((n-eaten n))
+        (seq-remove
+         (lambda (o)
+           (cond
+            ;; n-eaten has been eaten. Check here or later "<" comparison 
crashes.
+            ((not n-eaten)
+             ;; return nil because we always want things in m now.
+             nil
+             )
+            ;; we have a match so throw away the first element of n-eaten
+            ;; which we won't need again.
+            ((m-buffer-match-equal
+              (car n-eaten) o)
+             (progn
+               (setq n-eaten (seq-drop n-eaten 1))
+               t))
+            ;; we should discard also if n-eaten 1 is less than o because, both
+            ;; are sorted, so we will never match
+            ((<
+              ;; first half of the first match in n-eaten
+              (caar n-eaten)
+              ;; first half of match
+              (car o))
+             (progn
+               (setq n-eaten (seq-drop n-eaten 1))
+               t))))
+         m))
+    m))
+
+(defun m-buffer-in-match-p (matches position)
+  "Returns true is any of MATCHES contain POSITION."
+  (seq-some
+   (lambda (match)
+     (and
+      (<= (car match) position)
+      (<= position (cadr match))))
+   matches))
+;; #+end_src
+
+
+;; *** Partition
+
+;; Partition one set of markers by another. This is useful for finding matched
+;; pairs of markers.
+
+;; #+begin_src emacs-lisp
+(defun m-buffer--partition-by-marker(list partition)
+  "Given LIST, split at markers in PARTITION.
+
+This is the main implementation for `m-buffer-partition-by-marker',
+but assumes that partition starts with a very low value (or nil)."
+  (let* ((p-top (car-safe partition))
+         (p-val (car-safe (cdr-safe partition)))
+         (p-fn (lambda (n)
+                 (or (not p-val)
+                     (< n p-val)))))
+    (when list
+        (cons
+         (cons
+          p-top
+          (seq-take-while p-fn list))
+         (m-buffer--partition-by-marker
+          (seq-drop-while p-fn list)
+          (cdr partition))))))
+
+(defun m-buffer-partition-by-marker (list partition)
+  "Given LIST of markers, split at markers in PARTITION.
+Returns a list of lists. The first element of each list is nil or
+the marker from PARTITION. The rest of the elements are those
+elements in LIST which are at the same position or later in the
+buffer than the element from PARTITION, but before the next
+element from PARTITION.
+
+Both LIST and PARTITION must be sorted."
+  ;; TODO!
+  (m-buffer--partition-by-marker list (cons nil partition)))
+;; #+end_src
+
+
+;; ** Marker manipulation functions
+
+;; These functions do things to markers rather than the areas of the buffers
+;; indicated by the markers. This includes transforming between markers and
+;; integer positions, and niling markers explicitly, which prevents slow down
+;; before garbage collection.
+
+;; #+begin_src emacs-lisp
+(defun m-buffer-nil-marker (markers)
+  "Takes a (nested) list of MARKERS and nils them all.
+Markers slow buffer movement while they are pointing at a
+specific location, until they have been garbage collected. Niling
+them prevents this. See Info node `(elisp) Overview of Markers'."
+  (seq-map
+   (lambda (marker)
+     (if (seqp marker)
+         (m-buffer-nil-marker marker)
+       (set-marker marker nil)))
+   markers))
+
+(defun m-buffer-marker-to-pos (markers &optional postnil)
+  "Transforms a list of MARKERS to a list of positions.
+If the markers are no longer needed, set POSTNIL to true, or call
+`m-buffer-nil-marker' manually after use to speed future buffer
+movement. Or use `m-buffer-marker-to-pos-nil'."
+  (seq-map
+   (lambda (marker)
+     (prog1
+         (marker-position marker)
+       (when postnil
+         (set-marker marker nil))))
+   markers))
+
+(defun m-buffer-marker-to-pos-nil (markers)
+  "Transforms a list of MARKERS to a list of positions then nils.
+See also `m-buffer-nil-markers'"
+  (m-buffer-marker-to-pos markers t))
+
+(defun m-buffer-marker-tree-to-pos (marker-tree &optional postnil)
+  "Transforms a tree of markers to equivalent positions.
+MARKER-TREE is the tree.
+POSTNIL sets markers to nil afterwards."
+  (seq-map
+   (lambda (marker)
+     (if (seqp marker)
+         (m-buffer-marker-tree-to-pos marker postnil)
+       (prog1
+           (marker-position marker)
+         (when postnil
+           (set-marker marker nil)))))
+   marker-tree))
+
+(defun m-buffer-marker-tree-to-pos-nil (marker-tree)
+  "Transforms a tree of markers to equivalent positions.
+MARKER-TREE is the tree. Markers are niled afterwards."
+  (m-buffer-marker-tree-to-pos marker-tree t))
+
+(defun m-buffer-marker-clone (marker-tree &optional type)
+  "Return a clone of MARKER-TREE.
+The optional argument TYPE specifies the insertion type. See
+`copy-marker' for details."
+  (seq-map
+   (lambda (marker)
+     (if (seqp marker)
+         (m-buffer-marker-clone marker type)
+       (copy-marker marker type)))
+   marker-tree))
+
+(defun m-buffer-pos-to-marker (buffer positions)
+  "In BUFFER translates a list of POSITIONS to markers."
+  (seq-map
+   (lambda (pos)
+     (set-marker
+      (make-marker) pos buffer))
+   positions))
+;; #+end_src
+
+;; ** Replace, Delete, Extract
+
+;; #+begin_src emacs-lisp
+(defun m-buffer-replace-match (match-data replacement
+                                          &optional fixedcase literal subexp)
+  "Given a list of MATCH-DATA, replace with REPLACEMENT.
+If FIXEDCASE do not alter the case of the replacement text.
+If LITERAL insert the replacement literally.
+SUBEXP should be a number indicating the regexp group to replace.
+Returns markers to the start and end of the replacement. These
+markers are part of MATCH-DATA, so niling them will percolate backward.
+
+See also `replace-match'."
+  (save-excursion
+    (seq-map
+     (lambda (match)
+       (with-current-buffer
+           (marker-buffer (car match))
+         (save-match-data
+           (set-match-data match)
+           (replace-match
+            replacement fixedcase literal nil
+            (or subexp 0)))))
+     match-data))
+  ;; we have match-data
+  (m-buffer-match-nth-group (or subexp 0) match-data))
+
+(defun m-buffer-delete-match (match-data &optional subexp)
+  "Delete all MATCH-DATA.
+SUBEXP should be a number indicating the regexp group to delete.
+Returns markers to the start and end of the replacement. These
+markers are part of MATCH_DATA, so niling them will percolate backward."
+  (m-buffer-replace-match match-data "" subexp))
+
+(defun m-buffer-match-string (match-data &optional subexp)
+  "Return strings for MATCH-DATA optionally of group SUBEXP."
+  (seq-map
+   (lambda (match)
+     (with-current-buffer
+         (marker-buffer (car match))
+       (save-match-data
+         (set-match-data match)
+         (match-string
+          (or subexp 0)))))
+   match-data))
+
+(defun m-buffer-match-string-no-properties (match-data &optional subexp)
+  "Return strings for MATCH-DATA optionally of group SUBEXP.
+Remove all properties from return."
+  (seq-map
+   'substring-no-properties
+   (m-buffer-match-string
+    match-data subexp)))
+;; #+end_src
+
+;; ** Match Things
+
+;; Emacs comes with a set of in-built regexps most of which we use here.
+
+;; We define `m-buffer-apply-join' first. The reason for this function is that
+;; we want to take a list of match arguments and add to with, for instance, a
+;; regular expression. We need to add these at the end because most of our
+;; functions contain some positional arguments.
+
+
+;; #+begin_src emacs-lisp
+(defun m-buffer-apply-join (fn match &rest more-match)
+  (let*
+      ((args
+        (seq-take-while
+         (lambda (x) (not (keywordp x)))
+         match))
+       (pargs
+        (seq-drop-while
+         (lambda (x) (not (keywordp x)))
+         match))
+       (more-keywords
+        (seq-map
+         'car
+         (seq-partition more-match 2))))
+    (when
+        (seq-find
+         (lambda (keyword)
+           (plist-member pargs keyword))
+         more-keywords)
+      (error
+       "Match arg contradicts a defined argument."))
+    (apply fn (append args more-match pargs))))
+;; #+end_src
+
+;; For the following code, we use Emacs core regexps where possible.
+
+;; #+begin_src emacs-lisp
+(defun m-buffer-match-page (&rest match)
+  "Return a list of match data to all pages in MATCH.
+MATCH is of form BUFFER-OR-WINDOW MATCH-OPTIONS.  See
+`m-buffer-match' for further details."
+  (m-buffer-apply-join 'm-buffer-match
+                       match :regexp page-delimiter))
+;; #+end_src
+
+;; The `paragraph-separate' regexp can match an empty region, so we need to 
start
+;; each search at the beginning of the next line.
+
+;; #+begin_src emacs-lisp
+(defun m-buffer-match-paragraph-separate (&rest match)
+  "Return a list of match data to `paragraph-separate' in MATCH.
+MATCH is of form BUFFER-OR-WINDOW MATCH-OPTIONS.  See
+`m-buffer-match' for futher details."
+  (m-buffer-apply-join
+   'm-buffer-match match :regexp paragraph-separate
+   :post-match 'm-buffer-post-match-forward-line))
+
+(defvar m-buffer--line-regexp
+  "^.*$"
+  "Regexp to match a line.")
+
+(defun m-buffer-match-line (&rest match)
+  "Return a list of match data to all lines.
+MATCH is of the form BUFFER-OR-WINDOW MATCH-OPTIONS.
+See `m-buffer-match for further details."
+  (m-buffer-apply-join
+   'm-buffer-match
+   match :regexp m-buffer--line-regexp
+   :post-match 'm-buffer-post-match-forward-char))
+
+(defun m-buffer-match-line-start (&rest match)
+  "Return a list of match data to all line start.
+MATCH is of form BUFFER-OR-WINDOW MATCH-OPTIONS.  See
+`m-buffer-match' for further details."
+  (m-buffer-apply-join
+   'm-buffer-match-begin
+   match :regexp  "^"
+   :post-match 'm-buffer-post-match-forward-char))
+
+(defun m-buffer-match-line-end (&rest match)
+  "Return a list of match to line end.
+MATCH is of form BUFFER-OR-WINDOW MATCH-OPTIONS.  See
+`m-buffer-match' for further details."
+  (m-buffer-apply-join
+   'm-buffer-match-begin
+   match :regexp "$"
+   :post-match 'm-buffer-post-match-forward-char))
+;; #+end_src
+
+;; This is the first use of the =post-match= to terminate the loop, and was
+;; actually the motivation for adding it. We automatically terminate after the
+;; first match by simply returning nil.
+
+;; #+begin_src emacs-lisp
+(defun m-buffer-match-first (&rest match)
+  "Return the first match to MATCH.
+This matches more efficiently than matching all matches and
+taking the car. See `m-buffer-match' for further details of
+MATCH."
+  (m-buffer-apply-join
+   #'m-buffer-match match
+   :post-match (lambda () nil)))
+
+(defun m-buffer-match-first-line (&rest match)
+  "Return a match to the first line of MATCH.
+This matches more efficiently than matching all lines and taking
+the car.  See `m-buffer-match' for further details of MATCH."
+  (m-buffer-apply-join
+   'm-buffer-match-first match
+   :regexp m-buffer--line-regexp))
+
+(defun m-buffer-match-multi (regexps &rest match)
+  "Incrementally find matches to REGEXPS in MATCH.
+Finds the first match to the first element of regexps, then
+starting from the end of this match, the first match to the
+second element of regexps and so forth. See `m-buffer-match' for
+futher details of MATCH."
+  (when regexps
+      (let ((first-match
+             (m-buffer-apply-join
+              #'m-buffer-match-first
+              match
+              :regexp (car regexps))))
+        (append
+         first-match
+         (apply
+          #'m-buffer-match-multi
+          (cdr regexps)
+          (plist-put
+           match
+           :begin (car (m-buffer-match-end first-match))))))))
+;; #+end_src
+
+;; Emacs has a rather inconsistent interface here -- suddenly, we have a 
function
+;; rather than a variable for accessing a regexp.
+
+;; #+begin_src emacs-lisp
+(defun m-buffer-match-sentence-end (&rest match)
+  "Return a list of match to sentence end.
+MATCH is of the form BUFFER-OR-WINDOW MATCH-OPTIONS.  See
+`m-buffer-match' for further details."
+  (m-buffer-apply-join
+   'm-buffer-match-begin
+   match :regexp (sentence-end)))
+
+(defun m-buffer-match-word (&rest match)
+  "Return a list of match to all words.
+MATCH is of the form BUFFER-OR-WINDOW MATCH-OPTIONS.  See
+`m-buffer-match' for further details."
+  (m-buffer-apply-join
+   'm-buffer-match
+   match :regexp "\\\w+"))
+
+(defun m-buffer-match-empty-line (&rest match)
+  "Return a list of match to all empty lines.
+MATCH is of the form BUFFER-OR-WINDOW MATCH-OPTIONS.  See
+`m-buffer-match' for further details."
+  (m-buffer-apply-join
+   'm-buffer-match
+   match :regexp "^$"
+   :post-match 'm-buffer-post-match-forward-line))
+
+(defun m-buffer-match-non-empty-line (&rest match)
+  "Return a list of match to all non-empty lines.
+MATCH is fo the form BUFFER-OR-WINDOW MATCH-OPTIONS. See
+`m-buffer-match' for further details."
+  (m-buffer-apply-join
+   'm-buffer-match
+   match :regexp "^.+$"))
+
+(defun m-buffer-match-whitespace-line (&rest match)
+  "Return match data to all lines with only whitespace characters.
+Note empty lines are not included. MATCH is of form
+BUFFER-OR-WINDOW MATCH-OPTIONS. See `m-buffer-match' for
+further details."
+  (m-buffer-apply-join
+   'm-buffer-match
+   match :regexp "^\\s-+$"))
+
+;; #+end_src
+
+;; I don't think that there is a way to do this with regexps entirely, so we 
use
+;; substraction.
+
+;; #+begin_src emacs-lisp
+(defun m-buffer-match-non-whitespace-line (&rest match)
+  "Return match data to all lines with at least one non-whitespace character.
+Note empty lines do not contain any non-whitespace lines.
+MATCH is of form BUFFER-OR-WINDOW MATCH-OPTIONS. See
+`m-buffer-match' for further details."
+  (seq-difference
+   (apply 'm-buffer-match-line match)
+   (apply 'm-buffer-match-whitespace-line match)))
+
+;; Useful post-match functions
+(defun m-buffer-post-match-forward-line ()
+  "Attempt to move forward one line, return true if success."
+  (= 0 (forward-line)))
+
+(defun m-buffer-post-match-forward-char ()
+  "Attempts to move forward one char.
+Returns true if succeeds."
+  (condition-case _e
+      (progn
+        (forward-char)
+        t)
+    (error 'end-of-buffer
+           nil)))
+;; #+end_src
+
+
+;; ** Apply Function to Match
+
+;; These functions apply another function to some match-data. This is pretty
+;; useful generically, but also I use it for many of the following functions.
+
+;; #+begin_src emacs-lisp
+(defun m-buffer-on-region (fn match-data)
+  "Apply FN to MATCH-DATA.
+FN should take two args, the start and stop of each region.
+MATCH-DATA can be any list of lists with two elements (or more)."
+  (m-buffer-on-region-nth-group fn 0 match-data))
+
+(defun m-buffer-on-region-nth-group (fn n match-data)
+  "Apply FN to the Nth group of MATCH-DATA.
+FN should take two args, the start and stop of each region.
+MATCH-DATA can be any list of lists with two elements (or more)."
+  (seq-map
+   (lambda (x)
+     (apply fn x))
+   (m-buffer-match-nth-group n match-data)))
+;; #+end_src
+
+;; ** Overlay and Property Functions
+
+;; Adding properties or overlays to match-data. The functionality here somewhat
+;; overlaps with [[https://github.com/ShingoFukuyama/ov.el][ov.el]], which I 
didn't know about when I wrote this. It generally
+;; works over overlays, or regexps, while m-buffer works over match-data.
+
+;; #+begin_src emacs-lisp
+(defun m-buffer-overlay-match (match-data &optional front-advance rear-advance)
+  "Return an overlay for all match to MATCH-DATA.
+FRONT-ADVANCE and REAR-ADVANCE controls the borders of the
+overlay as defined in `make-overlay'.  Overlays do not scale that
+well, so use `m-buffer-propertize-match' if you intend to make
+and keep many of these.
+
+See Info node `(elisp) Overlays' for further information."
+  (let ((buffer (m-buffer-buffer-for-match match-data)))
+    (m-buffer-on-region
+     (lambda (beginning end)
+       (make-overlay
+        beginning end buffer
+        front-advance rear-advance))
+     match-data)))
+
+(defun m-buffer-add-text-property-match
+  (match-data properties)
+  "To MATCH-DATA add PROPERTIES.
+See `add-text-property' for details of the format of properties.
+Text properties are associated with the text and move with it. See
+Info node `(elisp) Text Properties' for further details."
+  (m-buffer-on-region
+   (lambda (beginning end)
+     (add-text-properties beginning end properties))
+   match-data))
+
+(defun m-buffer-put-text-property-match (match-data property value)
+  "To MATCH-DATA add PROPERTY wth VALUE.
+See `put-text-property' for details of the format of properties.
+Text properties are associated with the text and move with it. See
+Info node `(elisp) Text Properties' for further details."
+  (m-buffer-on-region
+   (lambda (beginning end)
+     (put-text-property beginning end property value))
+   match-data))
+
+(defun m-buffer-overlay-face-match (match-data face)
+  "To MATCH-DATA add FACE to the face property.
+This is for use in buffers which do not have function `font-lock-mode'
+enabled; otherwise use `m-buffer-overlay-font-lock-face-match'."
+  (seq-map
+   (lambda (ovly)
+     (overlay-put ovly 'face face))
+   (m-buffer-overlay-match match-data)))
+
+(defun m-buffer-overlay-font-lock-face-match (match-data face)
+  "To MATCH-DATA add FACE to the face property.
+This is for use in buffers which have variable `font-lock-mode' enabled;
+otherwise use `m-buffer-overlay-face-match'."
+  (seq-map
+   (lambda (ovly)
+     (overlay-put ovly 'face face))
+   (m-buffer-overlay-match match-data)))
+
+(defun m-buffer-text-property-face (match-data face)
+  "To MATCH-DATA apply FACE.
+This is for use in buffers which do
+not have variable `font-lock-mode' enabled; otherwise use
+`m-buffer-text-property-font-lock-face'."
+  (m-buffer-put-text-property-match match-data
+   'face face))
+
+(defun m-buffer-text-property-font-lock-face (match-data face)
+  "To MATCH-DATA apply FACE.
+This is for use in buffers which have variable `font-lock-mode'
+enabled; otherwise use `m-buffer-text-property-face'."
+  (m-buffer-put-text-property-match match-data
+   'font-lock-face face))
+
+(provide 'm-buffer)
+
+
+;;; m-buffer.el ends here
+;; #+end_src
diff --git a/test/lisp/tutorial-tests.el b/test/lisp/tutorial-tests.el
new file mode 100644
index 0000000..26cdb46
--- /dev/null
+++ b/test/lisp/tutorial-tests.el
@@ -0,0 +1,43 @@
+;;; tutorial-tests.el --- Test suite for tutorial  -*- lexical-binding: t; -*-
+
+;; Copyright (C) 2015-2017 Free Software Foundation, Inc.
+
+;; Author: Phillip Lord <address@hidden>
+;; Keywords: abbrevs
+
+;; This file is part of GNU Emacs.
+
+;; GNU Emacs is free software: you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation, either version 3 of the License, or
+;; (at your option) any later version.
+
+;; GNU Emacs is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;; GNU General Public License for more details.
+
+;; You should have received a copy of the GNU General Public License
+;; along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.
+
+;;; Code:
+
+(require 'ert)
+(require 'tutorial)
+
+(ert-deftest tutorial--open-tutorial ()
+  ;; We do not care about the return value (which happens to be nil),
+  ;; but it should not error.
+  (should-not
+   (let ((current-language-environment "English"))
+     (help-with-tutorial)))
+  (should-not
+   (let ((current-language-environment "Russian"))
+     (help-with-tutorial)))
+  (should-error
+   (let ((current-language-environment "Elvish"))
+     (help-with-tutorial))))
+
+
+(provide 'tutorial-tests)
+;;; tutorial-tests.el ends here



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