Additional output in Catch2

In Catch2 there is this feature where you can print some output only if a REQUIRE fails. It is useful to put there some state related information. It is done by using INFO macro.

For example, in a UnibitTrie data structure I have:

std::optional<Prefix> expected;
INFO(trie.ascii_string());
INFO("expected = " << sub);
INFO("it = " << it);
auto const it = trie.match_longest(sub);
REQUIRE((it != trie.end() == expected.has_value()));
if (expected)
    REQUIRE(it->prefix == expected);

This is very helpful when debugging - if the test fails I immediately see the iterator value and the trie, and I can figure out what I did wrong.

There is one surprising distinction between REQUIRE and INFO in how the arguments are turned to strings. The former uses Catch::StringMaker<T>, while the latter - ostream& operator<<(ostream&, T).