Mateusz Loskot :: hacking on, working out, living up

Compile-time unit tests

24 Oct 2009 | mloskot

Boost Build V2 includes testing module that provides nice features for running unit tests. A unit test run means a test builds and can be executed performing checks in run-time, however, a unit test can be also based on compilation or even linking result. Yet more surprisingly, sometimes a test is expected to not to compile and such failure is considered as success. It performs compile-time checking in design by contract.

In Generic Geometry Library, some tests use that feature of testing compilation result. For example, this way it’s possible to test the concepts in practice and to ensure that various constructs are not accepted by the library as expected by design.

For example, custom_linestring.cpp source file can be used to perform compile-time and run-time testing. If TEST_FAIL_APPEND is defined, unacceptable constructs are compiled and the compilation is expected to fail. If compiled without TEST_FAIL_APPEND defined, only acceptable code is enabled and regular run-time test performed.

Configuration of such thing is very easy with Boost Build V2. Here is Jamfile.v2 that performs the test for geometries in Generic Geometry Library using compile-fail rule:

<code>test-suite ggl-geometries
    [ compile-fail custom_linestring.cpp 
        : # requirements
        : # target name
    [ run custom_linestring.cpp ]

There are among others also rules like compile, link-fail and link.

The unit tests execution is simple:

mloskot@dog:~/dev/ggl/_svn/trunk/libs/ggl/test/geometries$ bjam | grep passed
**passed** bin/custom_linestring_test_fail_append.test/gcc-4.4.1/debug/custom_linestring_test_fail_append.test
**passed** bin/custom_linestring.test/gcc-4.4.1/debug/custom_linestring.test
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