Boost unit test: adding a helper method or private function

Question

I have a BOOST_AUTO_TEST_CASE which needs a helper function. I could just make this a regular function and call it from within; but I'd rather somehow keep it local and private to the scope of the BOOST_AUTO_CASE. I'd also like to be able to declare vars which are in the scope of both the test case and the helper functions (e.g. const int serverCount = 10;).

If the test case was a class (and not a macro), I'd simply use a private member function. How do I do this (or the equivalent) for a Boost unit test case?

Answer 1

Luckily there is a solution for this right in the Boost test framework: Fixtures. There are different types of fixtures but in your case the per test case fixture seems to fit.

#define BOOST_TEST_MODULE example
#include <boost/test/included/unit_test.hpp>

struct TestContext {
    TestContext() : testVar( 0 ) { BOOST_TEST_MESSAGE( "setup fixture" ); }
    ~TestContext()               { BOOST_TEST_MESSAGE( "teardown fixture" ); }

    int testVar;

    void helperMethod(int x, double y)
    {
        testVar = x * (int)y;
    }
};

BOOST_FIXTURE_TEST_CASE( test_case1, TestContext )
{
    BOOST_CHECK( testVar == 1 );
    ++testVar;
}

BOOST_FIXTURE_TEST_CASE( test_case2, TestContext )
{
    helperMethod(2, 3.1);
    // ...
}

testVar is accessible in the test case as well as in the TestContext class / struct. TestContext's constructor and destructor are called right before and after each test case respectively. They are not needed but can come in handy if you have to manage memory for example. In particular each test case is run with its own fresh instance of TestContext.

Update: Still valid for Boost 1.66, link updated.