Re: [Qemu-devel] [PATCH] docs: Add docs/devel/testing.rst

[Eric Blake]

On 01/28/2018 09:31 PM, Fam Zheng wrote:
> To make our efforts on QEMU testing easier to consume by contributors,
> let's add a document. For example, Patchew reports build errors on
> patches that should be relativly easy to reproduce with a few steps, and

s/relativly/relatively/

> it is much nicer if there is such a documentation that it can refer to.
> 
> This focues on how to run existing tests and how to write new test

s/focues/focuses/

> cases, without going into the frameworks themselves.
> 
> Signed-off-by: Fam Zheng <address@hidden>
> 
> ---
> 

I'll try not to repeat comments made by others...

> +This document describes the testing infrastructure in QEMU.
> +
> +"Make check" testings
> +=====================

s/testings/tests/, or 'Testing with "make check"'

> +
> +The "make check" testing family includes most of the C based tests in QEMU. 
> For
> +a quick help, run ``make check-help`` from the source tree.
> +
> +The usual way to run these tests is:
> +
> +.. code::
> +
> +  make check
> +
> +which includes QAPI schema tests, unit tests, and QTests. Different sub-types
> +of "make check" testings will be explained below.

s/testings/tests/

> +
> +Before running tests, it is best to build QEMU programs first. Some tests
> +expect the executables to exist and will fail with obscure messages if cannot
> +find them.

Should we fix 'make check' to depend on 'make all', so that we don't
have to require this?

> +
> +Unit tests
> +----------
> +
> +Unit tests, which can be invoked with ``make check-unit``, are simple C tests
> +that typically link to individual QEMU objects and exercise them by calling
> +into the modules.
> +
> +If you are writing new code in QEMU, consider adding a unit test, especially
> +for utility modules that are relatively stateless or have few dependencies. 
> To
> +add a new unit test:
> +
> +1. Create a new source file. For example, ``tests/test-foo.c``.
> +
> +2. Write the test. Normally you would include the headers file which exports
> +   the module API, then verify the interface behaves as expected from your
> +   test. The test code should be organized with the glib testing framework.
> +   Copy and modify an existing test is usually a good idea.
> +
> +3. Add the test to ``tests/Makefile.include``. First, name the unit test
> +   program and add it to ``$(check-unit-y)``; then add a rule to build the
> +   executable. Optionally, you can add a magical variable to support 
> ``gcov``.
> +   For example:
> +
> +.. code::
> +
> +  check-unit-y += tests/test-foo$(EXESUF)
> +  tests/test-foo$(EXESUF): tests/test-foo.o $(test-util-obj-y)
> +  ...
> +  gcov-files-test-foo-y = util/foo.c

Is it worth documenting that you can often run 'gdb ./test-foo' after
the fact for a failing test?  (Most unit tests don't require any magic
environment variables to be set)

> +
> +QTest
> +-----
> +
> +QTest is a testing framework that simplifies starting QEMU and interacting 
> with
> +the virtual machine just like a guest kernel does. It can be very useful to
> +test hardware emulation, for example; it could also control certain aspects 
> of
> +QEMU (such as virtual clock stepping), with a specially purposed "qtest"
> +protocol. Refer to the documentation in ``qtest.c`` file for more details of
> +the protocol.
> +
> +QTest cases can be executed with
> +
> +.. code::
> +
> +   make check-qtest
> +
> +The QTest library is implemented by ``tests/libqtest.c`` and the API is 
> defined
> +in ``tests/libqtest.h``.
> +
> +Consider adding a new QTest case when you are introducing a new virtual
> +hardware, or extending one if you are adding functionalities to an existing
> +virtual device.
> +
> +On top of libqtest, a higher level library, ``libqos``, was created to
> +encapsulate common tasks of device drivers, such as memory management and
> +communicating with system buses or devices. Many virtual device tests use
> +libqos instead of directly calling into libqos.
> +
> +Steps to add a new QTest case are:
> +
> +1. Create a new source file for the test. (More than one file can be added as
> +   necessary.) For example, ``tests/test-foo-device.c``.  2. Write the test
> +   code with the glib and libqtest/libqos API. See also existing tests and 
> the
> +   library headers for reference.
> +
> +3. Register the new test in ``tests/Makefile.include``. Add the test 
> executable
> +   name to an appropriate ``check-qtest-*-y`` variable. For example:
> +
> +   ``check-qtest-generic-y = tests/test-foo-device$(EXESUF)``
> +
> +4. Add object dependencies of the executable in the Makefile, including the
> +   test source file(s) and other interesting objects. For example:
> +
> +   ``tests/test-foo-device$(EXESUF): tests/test-foo-device.o 
> $(libqos-obj-y)``

Is it worth documenting that 'make check-qtest' runs EVERY test unless
you define magic environment variables; and if it fails, running 'make
check-qtest V=1' can help identify which test failed?  Here, running a
mere 'gdb foo-device-test' is prone to fail (because it is missing magic
environment variables); it's possible to run individual tests under gdb
but it requires more effort (among other things, the V=1 helps you learn
what environment variables to set).

> +

> +Docker based testing
> +====================

'Docker based tests' or 'Testing with docker'

> +
> +Introduction
> +------------
> +
> +Docker testing framework in QEMU utilizes the public Docker images to build 
> and

s/^Docker/The Docker/
s/the public/public/

> +test QEMU in predefined and widely accessible Linux environments.  This makes
> +it possible to expand the test coverage across distros, toolchain flavors and
> +library versions.
> +


-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org

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