Unit Tests in GlusterFS


Art-of-unittesting provides a good definition for unit tests. A good unit test is:

  • Able to be fully automated
  • Has full control over all the pieces running (Use mocks or stubs to achieve this isolation when needed)
  • Can be run in any order if part of many other tests
  • Runs in memory (no DB or File access, for example)
  • Consistently returns the same result (You always run the same test, so no random numbers, for example. save those for integration or range tests)
  • Runs fast
  • Tests a single logical concept in the system
  • Readable
  • Maintainable
  • Trustworthy (when you see its result, you don’t need to debug the code just to be sure)


GlusterFS unit test framework is based on cmocka. cmocka provides developers with methods to isolate and test modules written in C language. It also provides integration with Jenkins by providing JUnit XML compliant unit test results.


Running Unit Tests

To execute the unit tests, all you need is to type make check. Here is a step-by-step example assuming you just cloned a GlusterFS tree:

$ ./autogen.sh
$ ./configure --enable-debug
$ make check

Sample output:

PASS: mem_pool_unittest
Testsuite summary for glusterfs 3git
# TOTAL: 1
# PASS:  1
# SKIP:  0
# XFAIL: 0
# FAIL:  0
# XPASS: 0
# ERROR: 0

In this example, mem_pool_unittest has multiple tests inside, but make check assumes that the program itself is the test, and that is why it only shows one test. Here is the output when we run mem_pool_unittest directly:

$ ./libglusterfs/src/mem_pool_unittest
[==========] Running 10 test(s).
[ RUN      ] test_gf_mem_acct_enable_set
Expected assertion data != ((void *)0) occurred
[       OK ] test_gf_mem_acct_enable_set
[ RUN      ] test_gf_mem_set_acct_info_asserts
Expected assertion xl != ((void *)0) occurred
Expected assertion size > ((4 + sizeof (size_t) + sizeof (xlator_t *) + 4 + 8) + 8) occurred
Expected assertion type <= xl->mem_acct.num_types occurred
[       OK ] test_gf_mem_set_acct_info_asserts
[ RUN      ] test_gf_mem_set_acct_info_memory
[       OK ] test_gf_mem_set_acct_info_memory
[ RUN      ] test_gf_calloc_default_calloc
[       OK ] test_gf_calloc_default_calloc
[ RUN      ] test_gf_calloc_mem_acct_enabled
[       OK ] test_gf_calloc_mem_acct_enabled
[ RUN      ] test_gf_malloc_default_malloc
[       OK ] test_gf_malloc_default_malloc
[ RUN      ] test_gf_malloc_mem_acct_enabled
[       OK ] test_gf_malloc_mem_acct_enabled
[ RUN      ] test_gf_realloc_default_realloc
[       OK ] test_gf_realloc_default_realloc
[ RUN      ] test_gf_realloc_mem_acct_enabled
[       OK ] test_gf_realloc_mem_acct_enabled
[ RUN      ] test_gf_realloc_ptr
Expected assertion ((void *)0) != ptr occurred
[       OK ] test_gf_realloc_ptr
[==========] 10 test(s) run.
[  PASSED  ] 10 test(s).
[  FAILED  ] 0 test(s).
[  REPORT  ] Created libglusterfs_mem_pool_xunit.xml report

Writing Unit Tests

Enhancing your C functions

Programming by Contract

Add the following to your C file:

#include <cmocka_pbc.h>
 * Programming by Contract is a programming methodology
 * which binds the caller and the function called to a
 * contract. The contract is represented using Hoare Triple:
 *      {P} C {Q}
 * where {P} is the precondition before executing command C,
 * and {Q} is the postcondition.
 * See also:
 * http://en.wikipedia.org/wiki/Design_by_contract
 * http://en.wikipedia.org/wiki/Hoare_logic
 * http://dlang.org/dbc.html
 #ifndef CMOCKERY_PBC_H_

#if defined(UNIT_TESTING) || defined (DEBUG)

#include <assert.h>

 * Checks caller responsibility against contract
#define REQUIRE(cond) assert(cond)

 * Checks function reponsability against contract.
#define ENSURE(cond) assert(cond)

 * While REQUIRE and ENSURE apply to functions, INVARIANT
 * applies to classes/structs.  It ensures that intances
 * of the class/struct are consistent. In other words,
 * that the instance has not been corrupted.
#define INVARIANT(invariant_fnc) do{ (invariant_fnc) } while (0);

#define REQUIRE(cond) do { } while (0);
#define ENSURE(cond) do { } while (0);
#define INVARIANT(invariant_fnc) do{ } while (0);

#endif /* defined(UNIT_TESTING) || defined (DEBUG) */
#endif /* CMOCKERY_PBC_H_ */

This is an extremely simple example:

int divide (int n, int d)
    int ans;

    REQUIRE(d != 0);

    ans = n / d;

    // As code is added to this function throughout its lifetime,
    // ENSURE will assert that data will be returned
    // according to the contract.  Again this is an
    // extremely simple example. :-D
    ENSURE( ans == (n / d) );

    return ans;

Important Note

REQUIRE, ENSURE, and INVARIANT are only available when DEBUG or UNIT_TESTING are set in the CFLAGS. You must pass --enable-debug to ./configure to enable PBC on your non-unittest builds.

Overriding functions

Cmockery2 provides its own memory allocation functions which check for buffer overrun and memory leaks. The following header file must be included last to be able to override any of the memory allocation functions:

#include <cmocka.h>

This file will only take effect with the UNIT_TESTING CFLAG is set.

Creating a unit test

Once you identify the C file you would like to test, first create a unittest directory under the directory where the C file is located. This will isolate the unittests to a different directory.

Next, you need to edit the Makefile.am file in the directory where your C file is located. Initialize the Makefile.am if it does not already have the following sections:

#### UNIT TESTS #####
CLEANFILES += *.gcda *.gcno *_xunit.xml
noinst_PROGRAMS =

Now you can add the following for each of the unit tests that you would like to build:

### UNIT TEST xxx_unittest ###
xxx_unittest_CPPFLAGS = $(xxx_CPPFLAGS)
xxx_unittest_SOURCES = xxx.c \
xxx_unittest_CFLAGS = $(UNITTEST_CFLAGS)
noinst_PROGRAMS += xxx_unittest
TESTS += xxx_unittest

Where xxx is the name of your C file. For example, look at libglusterfs/src/Makefile.am.

Copy the simple unit test from the [cmocka API][cmockaapi] to unittest/xxx_unittest.c. If you would like to see an example of a unit test, please refer to libglusterfs/src/unittest/mem_pool_unittest.c.


You may see that the linker will complain about missing functions needed by the C file you would like to test. Identify the required functions, then place their stubs in a file called unittest/xxx_mock.c, then include this file in Makefile.am in xxx_unittest_SOURCES. This will allow you to you Cmockery2's mocking functions.

Running the unit test

You can type make in the directory where the C file is located. Once you built it and there are no errors, you can execute the test either by directly executing the program (in our example above it is called xxx_unittest ), or by running make check.


Sometimes you may need to debug your unit test. To do that, you will have to point gdb to the binary which is located in the same directory as the source. For example, you can do the following from the root of the source tree to debug mem_pool_unittest:

$ gdb libglusterfs/src/mem_pool_unittest