[PATCH v3 54/54] docs/devel: testing: Document writing portable test cases

[Bin Meng]

From: Bin Meng <bin.meng@windriver.com>

Update the best practices of how to write portable test cases that
can be built and run successfully on both Linux and Windows hosts.

Signed-off-by: Bin Meng <bin.meng@windriver.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
---

(no changes since v3)

Changes in v2:
- Minor wording changes
- Drop patches that were already applied in the mainline
- Drop patch: "qga/commands-posix-ssh: Use g_mkdir_with_parents()"
- Drop patch: "tests: Skip iotests and qtest when '--without-default-devices'"
- Drop patch: "tests/qtest: Fix ERROR_SHARING_VIOLATION for win32"

 docs/devel/testing.rst | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/docs/devel/testing.rst b/docs/devel/testing.rst
index aea5b42356..0eae9c4654 100644
--- a/docs/devel/testing.rst
+++ b/docs/devel/testing.rst
@@ -115,6 +115,36 @@ check-block
 are in the "auto" group).
 See the "QEMU iotests" section below for more information.
 
+Writing portable test cases
+~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Both unit tests and qtests can run on POSIX hosts as well as a Windows host.
+Care must be taken when writing portable test cases that can be built and run
+successfully on various hosts. The following are some best practices:
+
+* Use portable APIs from glib whenever necessary, e.g.: g_setenv(),
+  g_mkdtemp(), g_mkdir().
+* Avoid using hardcoded /tmp for temporary file directory.
+  Use g_get_tmp_dir() instead.
+* Bear in mind that Windows has different special string representation for
+  stdin/stdout/stderr and null devices. For example if your test case uses
+  "/dev/fd/2" and "/dev/null" on Linux, remember to use "2" and "nul" on
+  Windows instead. Also IO redirection does not work on Windows, so avoid
+  using "2>nul" whenever necessary.
+* If your test cases uses the blkdebug feature, use relative path to pass
+  the config and image file paths in the command line as Windows absolute
+  path contains the delimeter ":" which will confuse the blkdebug parser.
+* Use double quotes in your extra QEMU commmand line in your test cases
+  instead of single quotes, as Windows does not drop single quotes when
+  passing the command line to QEMU.
+* Windows opens a file in text mode by default, while a POSIX compliant
+  implementation treats text files and binary files the same. So if your
+  test cases opens a file to write some data and later wants to compare the
+  written data with the original one, be sure to pass the letter 'b' as
+  part of the mode string to fopen(), or O_BINARY flag for the open() call.
+* If a certain test case can only run on POSIX or Linux hosts, use a proper
+  #ifdef in the codes. If the whole test suite cannot run on Windows, disable
+  the build in the meson.build file.
+
 QEMU iotests
 ------------
 
-- 
2.34.1