compat.doctest

// Behavioral test — compat.doctest gives a working framework AND its main.
//
// No `import std;` here: doctest.h is a textual header that includes the C++
// standard headers itself, and mixing those with the std module is the one
// thing this index's module packages tell consumers not to do.
//
// A failing REQUIRE makes doctest return a non-zero exit code, which is how
// `mcpp test` sees it — so the assertions below are the test, and the runner
// needs no adapter.
#define DOCTEST_CONFIG_IMPLEMENT_WITH_MAIN
#include <doctest/doctest.h>

#include <string>
#include <vector>

static unsigned factorial(unsigned n) { return n <= 1 ? 1 : n * factorial(n - 1); }

TEST_CASE("factorial") {
    CHECK(factorial(0) == 1);
    CHECK(factorial(5) == 120);
}

// …