Module fluid::wiki::theory

A #[theory] is a test more complex than a fact, that must be proven or inferred with multiple cases.

Therefore, a theory must come with its multiple test cases, for example:

#[theory]
#[case("Cerberus", 3)]
#[case("Hydra", 7)]
#[case("Janus", 2)]
#[case("A regular dice", 6)]
#[case("Normal guy", 1)]
fn each_creature_has_a_correct_number_of_faces(name: &str, nbr_faces: u8) {
    number_of_faces(name).should().be_equal_to(nbr_faces);
}

If the test fails, it displays a nice error message:

failures:

---- each_creature_has_a_correct_number_of_faces::case_A_regular_dice_6 stdout ----
The test failed at src/main.rs:14, for the case name = "A regular dice", nbr_faces = 6:
    number_of_faces ( name ) has the value 1.
    It should be equal to 6 but it is not.

It is possible to use standard assertions inside of the theory function, but it makes few sense, because without should(), there would be no prettified error message nor case information in case of failed test.