BOOST_level_EXCEPTION(expression, exception, predicate) asserts that when expression throws an exception of type exception, the predicate applied to the instance of the exception returns true. This is used to verify not only that an exception of the correct type was thrown, but that the contents of the thrown exception meet the expectations of the predicate.

The predicate can return bool, or predicate_result which allows the predicate to build up a detailed failure message.

Example

class error_number_exception
{
public:
    error_number_exception(int num)
        : num_(num)
    { }

    int error_number() const { return num_; }

private:
    int num_;
};

static bool has_error_number_1(error_number_exception const& ex)
{
    return ex.error_number() == 1;
}

BOOST_AUTO_TEST_CASE(example_exception)
{
    BOOST_REQUIRE_EXCEPTION(throw error_number_exception(1),
        error_number_exception, has_error_number_1);
}