From 94dab75b56f0bcfa8389c6befe3d4be3fbb3c75e Mon Sep 17 00:00:00 2001 From: Mathieu Desnoyers Date: Wed, 19 Nov 2014 22:40:27 +0100 Subject: [PATCH] Document test anti-patterns MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit Signed-off-by: Mathieu Desnoyers Signed-off-by: Jérémie Galarneau --- tests/Makefile.am | 2 +- tests/README | 63 +++++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 64 insertions(+), 1 deletion(-) create mode 100644 tests/README diff --git a/tests/Makefile.am b/tests/Makefile.am index c14e733a3..2f1f1c38b 100644 --- a/tests/Makefile.am +++ b/tests/Makefile.am @@ -15,7 +15,7 @@ if USE_PYTHON endif dist_noinst_SCRIPTS = run.sh unit_tests fast_regression long_regression root_regression with_bindings_regression -EXTRA_DIST = run.sh unit_tests fast_regression long_regression root_regression with_bindings_regression +EXTRA_DIST = run.sh unit_tests fast_regression long_regression root_regression with_bindings_regression README all-local: @if [ x"$(srcdir)" != x"$(builddir)" ]; then \ diff --git a/tests/README b/tests/README new file mode 100644 index 000000000..fc8630cda --- /dev/null +++ b/tests/README @@ -0,0 +1,63 @@ +* Test Anti-Patterns + +OK, there are a few patterns that have been found over and over in the +testing code base which makes the tests flaky. Here is an incomplete +list. Don't do that. + +1) Using pidof to wait for a background application (by name) to + disappear. + + Why is it flaky ? + + The application may be delayed after being forked, but not executed + yet. Therefore, pidof will not find it. Use "wait" instead. + +2) Using sleep as delay-based optimistic synchronization technique. + + Why is it flaky ? + + Everything that needs to happen before/after other things need to + be explicitly synchronized using e.g. a file (used as a flag). + Sleep is just an indicator of a minimum arbitrary delay, but + machine load and scheduling can actually mess up the real delay + between applications. Use explicit synchronization points. Never + sleep. + +3) Using killall on a background application. + + Why is it flaky ? + + Similarly to pidof, killall may run before the background application + executes, thus failing to find it. Store the application PID after it + it launched in background into a temporary variable for later use + by kill and wait. + +4) Using wait ${!} to wait for completion of many background + applications. + + Why is it flaky ? + + It just waits for the last application put in background. Use + "wait" to wait for all background applications. + +5) Forgetting wait at the end (or error return path) of a test phase + that has background applications. + + Why is it flaky ? + + Those application may interact with the following testing phases, + thus skewing the results. + +6) Not grepping into the entire code base for similar patterns. + + When you find a problematic coding pattern, chances are it appears + elsewhere in the testing code base. Please fix it everywhere! + +7) Introducing a utility abstraction without changing all open coded + similar code path. + + When an abstraction for e.g. starting and stopping the session daemon + is introduced as a utility (e.g. utils.sh), future changes will + assume that all the testing code base is using this abstraction. + Leaving a few custom open-coded sites of duplicated code around is a + good way to make it a pain to update the abstraction in the future. -- 2.34.1