multipath-tools unit tests

Unit tests are built and run by running make test in the top directory, or simply make in the tests subdirectory. The test output is saved as <testname>.out. The test programs are called <testname>-test, and can be run standalone e.g. for debugging purposes.

Notes on individual tests

Tests that require root permissions

The following tests must be run as root, otherwise some test items will be skipped because of missing permissions, or the test will fail outright:

• dmevents
• directio (if DIO_TEST_DEV is set, see below)

To run these tests, after building the tests as non-root user, change to the tests directory and run make test-clean; then run make again as root.

directio test

This test includes test items that require a access to a block device. The device will be opened in read-only mode; you don't need to worry about data loss. However, the user needs to specify a device to be used. Set the environment variable DIO_TEST_DEV to the path of the device. Alternatively, create a file directio_test_dev under the tests directory containting a single line that sets this environment variable in Bourne Shell syntax, like this:

DIO_TEST_DEV=/dev/sdc3

After that, run make directio.out as root in the tests directory to perform the test.

Adding tests

The unit tests are based on the cmocka test framework, and make use of cmocka's "mock objects" feature to simulate how the code behaves for different input values. cmocka achieves this by modifying the symbol lookup at link time, substituting "wrapper functions" for the originally called function. The Makefile contains code to make sure that __wrap_xyz() wrapper functions are automatically passed to the linker with matching -Wl,--wrap command line arguments, so that tests are correctly rebuilt if wrapper functions are added or removed.

Making sure symbol wrapping works: OBJDEPS

Special care must be taken to wrap function calls inside a library. Suppose you want to wrap a function which is both defined in libmultipath and called from other functions in libmultipath, such as checker_check(). When libmultipath.so is created, the linker resolves calls to checker_check() inside the .so file. When later the test executable is built by linking the test object file with libmultipath.so, these calls can't be wrapped any more, because they've already been resolved, and wrapping works only for unresolved symbols. Therefore, object files from libraries that contain calls to functions which need to be wrapped must be explicitly listed on the linker command line in order to make the wrapping work. To enforce this, add these object files to the xyz-test_OBJDEPS variable in the Makefile.

Using wrapper function libraries: TESTDEPS

Some wrapper functions are useful in multiple tests. These are maintained in separate input files, such as test-lib.c or test-log.c. List these files in the xyz-test_TESTDEPS variable for your test program if you need these wrappers.

Specifying library dependencies: LIBDEPS

In order to keep the tests lean, not all libraries that libmultipath normally pulls in are used for every test. Add libraries you need (such as -lpthread) to the xyz-test_LIBDEPS variable.