[C++] Boost test: catch user defined exceptions

Question

If I have user defined exceptions in my code, I can't get Boost test to consider them as failures.

For example,

BOOST_AUTO_TEST_CASE_EXPECTED_FAILURES(MyTest,1)
BOOST_AUTO_TEST_CASE(MyTest)
{
// code which throws user defined exception, not derived from std::exception.

}

I get a generic message:

Caught exception: ....
unknown location(0):....

It does not recognize this error as a failure since it is not a std::exception. So it does not honor the expected_failures clause.

How do I enforce that the piece of code should always throw an exception? THis seems to be a useful thing to want. In case future code changes cause the code to pass and the exception is not thrown, I want to know that.

Answer 1

The EXPECTED_FAILURES are referring to failures against BOOST_REQUIRE or other assertions. The documentation clearly states:

The feature is not intended to be used to check for expected functionality failures. To check that a particular input is causing an exception to be thrown use BOOST_CHECK_THROW family of testing tools.

Emphasis was mine.

The expected failures are meant to be used as a temporary workaround during testing when an assertion is failing but you want to temporarily ignore it.

Taking a snippet from their expected failures spec:

BOOST_AUTO_TEST_CASE_EXPECTED_FAILURES( my_test1, 1 )

BOOST_AUTO_TEST_CASE( my_test1 )
{
    BOOST_CHECK( 2 == 1 );
}

will result in output of

test.cpp(10): error in "my_test1": check 2 == 1 failed

Test suite "example" passed with:
  1 assertions out of 1 failed
  1 failures expected
  1 test case out of 1 passed

As you can see, in spite of assertions failing, the test case still passed due to the use of expected failures.

---

So if you need to verify that something is throwing an exception, you use code like the following:

BOOST_AUTO_TEST_CASE(invalid_operation_should_throw_custom_exception)
{
    MyObj obj;
    BOOST_REQUIRE_THROW(obj.invalid_operation(), CustomException);
}