Feature request: check for exception string (like Catch's CHECK_THROWS_WITH)

[nlohmann]

Description

I would like to have a macro equivalent to Catch's CHECK_THROWS_WITH, see https://github.com/philsquared/Catch/blob/master/docs/assertions.md#exceptions.

Currently, I would need to provide a try/catch block on my own and call CHECK on the exception's what() function.

[onqtam]

Matchers are on the roadmap but I won't have the time to implement them properly in the next 2-3 months - just signed a 3 month contract to get some cash... Until then you could use this solution:

#include "doctest.h"

#include <stdexcept>

#define DOCTEST_EXT_THROWS_WITH_IMPL(the_assert, expr, message)                                    \
    do {                                                                                           \
        doctest::String _doctest_exception_string = "Didn't throw at all";                         \
        try {                                                                                      \
            expr;                                                                                  \
        } catch(std::exception & e) { _doctest_exception_string = e.what(); } catch(...) {         \
            _doctest_exception_string = "Unknown exception";                                       \
        }                                                                                          \
        DOCTEST_EXPAND_VA_ARGS(the_assert)(_doctest_exception_string == doctest::String(message)); \
    } while((void)0, 0)

#define CHECK_THROWS_WITH(expr, message) DOCTEST_EXT_THROWS_WITH_IMPL(DOCTEST_CHECK, expr, message)
#define REQUIRE_THROWS_WITH(expr, message) DOCTEST_EXT_THROWS_WITH_IMPL(DOCTEST_REQUIRE, expr, message)

TEST_CASE("using a custom exception assert macro") {
    CHECK_THROWS_WITH(throw std::runtime_error("omg"), "omg 2!!!");
    REQUIRE_THROWS_WITH(throw std::runtime_error("wtf"), "wtf");
    CHECK_THROWS_WITH(throw 5, "wtf");
    CHECK_THROWS_WITH(((void)0), "wtf");
}

the output message will contain the exception result and what was expected - its not perfect, but should do the trick

[nlohmann]

Any news on this?

[onqtam]

This is a high priority feature. I'll try to get version 2.1 out by the end of the year but cannot promise it - will notify here when done. Thanks for waiting.

[onqtam]

This is now in the master branch - version 2.1.0 is released! Thanks for the patience!

So currently you can pass only C strings to the <LEVEL>_THROWS_WITH macros - like this:

CHECK_THROWS_WITH(do_parsing(), "bad parse!");

In the future support for matchers will be added (the ability to use objects instead of just plain old C strings) but the interface of the macros will not change.

Currently the framework translates exceptions deriving from std::exception and calls the .what() method for them. Also C strings are supported as exceptions. The framework can be extended with user-defined exceptions as well - consult the docs:

https://github.com/onqtam/doctest/blob/master/doc/markdown/stringification.md#translating-exceptions

I also did a small change in version 2.1 to allow 2 ways of passing exception types to _THROWS_AS - with and without a reference (but the result is always catch by reference) so it is easier to migrate: 8cf9041

Let me know if you need anything else.

[onqtam]

@nlohmann aaand a bit unrelated to this issue, but I just released version 2.2 and now the DOCTEST_CONFIG_SUPER_FAST_ASSERTS config option also affects the normal asserts and not just the binary - see the results in the benchmarks