15.2 Simple Tests using ‘parallel-tests’

The option parallel-tests (see Options) enables a test suite driver that is mostly compatible to the simple test driver described in the previous section, but provides a few more features and slightly different semantics. It features concurrent execution of tests with make -j, allows to specify inter-test dependencies, lazy reruns of tests that have not completed in a prior run, summary and verbose output in ‘RST’ (reStructuredText) and ‘HTML’ format, and hard errors for exceptional failures. Similar to the simple test driver, TESTS_ENVIRONMENT, AM_COLOR_TESTS, XFAIL_TESTS, and the check_* variables are honored, and the environment variable srcdir is set during test execution.

This test driver is still experimental and may undergo changes in order to satisfy additional portability requirements.

The driver operates by defining a set of make rules to create a summary log file, TEST_SUITE_LOG, which defaults to test-suite.log and requires a .log suffix. This file depends upon log files created for each single test program listed in TESTS, which in turn contain all output produced by the corresponding tests.

Each log file is created when the corresponding test has completed. The set of log files is listed in the read-only variable TEST_LOGS, and defaults to TESTS, with the executable extension if any (see EXEEXT), as well as any suffix listed in TEST_EXTENSIONS removed, and .log appended. TEST_EXTENSIONS defaults to .test. Results are undefined if a test file name ends in several concatenated suffixes.

For tests that match an extension .ext listed in TEST_EXTENSIONS, you can provide a test driver using the variable ext_LOG_COMPILER (note the upper-case extension) and pass options in AM_ext_LOG_FLAGS and allow the user to pass options in ext_LOG_FLAGS. It will cause all tests with this extension to be called with this driver. For all tests without a registered extension, the variables LOG_COMPILER, AM_LOG_FLAGS, and LOG_FLAGS may be used. For example,

     TESTS = foo.pl bar.py baz
     TEST_EXTENSIONS = .pl .py
     PL_LOG_COMPILER = $(PERL)
     AM_PL_LOG_FLAGS = -w
     PY_LOG_COMPILER = $(PYTHON)
     AM_PY_LOG_FLAGS = -v
     LOG_COMPILER = ./wrapper-script
     AM_LOG_FLAGS = -d

will invoke ‘$(PERL) -w foo.pl’, ‘$(PYTHON) -v bar.py’, and ‘./wrapper-script -d baz’ to produce foo.log, bar.log, and baz.log, respectively. The ‘TESTS_ENVIRONMENT’ variable is still expanded before the driver, but should be reserved for the user.

As with the simple driver above, by default one status line is printed per completed test, and a short summary after the suite has completed. However, standard output and standard error of the test are redirected to a per-test log file, so that parallel execution does not produce intermingled output. The output from failed tests is collected in the test-suite.log file. If the variable ‘VERBOSE’ is set, this file is output after the summary. For best results, the tests should be verbose by default now.

With make check-html, the log files may be converted from RST (reStructuredText, see http://docutils.sourceforge.net/rst.html) to HTML using ‘RST2HTML’, which defaults to rst2html or rst2html.py. The variable ‘TEST_SUITE_HTML’ contains the set of converted log files. The log and HTML files are removed upon make mostlyclean.

Even in the presence of expected failures (see XFAIL_TESTS, there may be conditions under which a test outcome needs attention. For example, with test-driven development, you may write tests for features that you have not implemented yet, and thus mark these tests as expected to fail. However, you may still be interested in exceptional conditions, for example, tests that fail due to a segmentation violation or another error that is independent of the feature awaiting implementation. Tests can exit with an exit status of 99 to signal such a hard error. Unless the variable DISABLE_HARD_ERRORS is set to a nonempty value, such tests will be counted as failed.

By default, the test suite driver will run all tests, but there are several ways to limit the set of tests that are run:

• You can set the TESTS variable, similarly to how you can with the simple test driver from the previous section. For example, you can use a command like this to run only a subset of the tests:

            env TESTS="foo.test bar.test" make -e check
  

• You can set the TEST_LOGS variable. By default, this variable is computed at make run time from the value of TESTS as described above. For example, you can use the following:

            set x subset*.log; shift
            env TEST_LOGS="foo.log $*" make -e check
  

• By default, the test driver removes all old per-test log files before it starts running tests to regenerate them. The variable RECHECK_LOGS contains the set of log files which are removed. RECHECK_LOGS defaults to TEST_LOGS, which means all tests need to be rechecked. By overriding this variable, you can choose which tests need to be reconsidered. For example, you can lazily rerun only those tests which are outdated, i.e., older than their prerequisite test files, by setting this variable to the empty value:

            env RECHECK_LOGS= make -e check
  

• You can ensure that all tests are rerun which have failed or passed unexpectedly, by running make recheck in the test directory. This convenience target will set RECHECK_LOGS appropriately before invoking the main test driver. The recheck-html target does the same as recheck but again converts the resulting log file in HTML format, like the check-html target.

In order to guarantee an ordering between tests even with make -jN, dependencies between the corresponding log files may be specified through usual make dependencies. For example, the following snippet lets the test named foo-execute.test depend upon completion of the test foo-compile.test:

     TESTS = foo-compile.test foo-execute.test
     foo-execute.log: foo-compile.log

Please note that this ordering ignores the results of required tests, thus the test foo-execute.test is run even if the test foo-compile.test failed or was skipped beforehand. Further, please note that specifying such dependencies currently works only for tests that end in one of the suffixes listed in TEST_EXTENSIONS.

Tests without such specified dependencies may be run concurrently with parallel make -jN, so be sure they are prepared for concurrent execution.

The combination of lazy test execution and correct dependencies between tests and their sources may be exploited for efficient unit testing during development. To further speed up the edit-compile-test cycle, it may even be useful to specify compiled programs in EXTRA_PROGRAMS instead of with check_PROGRAMS, as the former allows intertwined compilation and test execution (but note that EXTRA_PROGRAMS are not cleaned automatically, see Uniform).

The variables TESTS and XFAIL_TESTS may contain conditional parts as well as configure substitutions. In the latter case, however, certain restrictions apply: substituted test names must end with a nonempty test suffix like .test, so that one of the inference rules generated by automake can apply. For literal test names, automake can generate per-target rules to avoid this limitation.

Please note that it is currently not possible to use $(srcdir)/ or $(top_srcdir)/ in the TESTS variable. This technical limitation is necessary to avoid generating test logs in the source tree and has the unfortunate consequence that it is not possible to specify distributed tests that are themselves generated by means of explicit rules, in a way that is portable to all make implementations (see Make Target Lookup, the semantics of FreeBSD and OpenBSD make conflict with this). In case of doubt you may want to require to use GNU make, or work around the issue with inference rules to generate the tests.