Macro assert_that

macro_rules! assert_that {
    ($actual:expr, [ $($expected:expr),* ] $(,)?) => { ... };
    ($actual:expr, { $($expected:expr),* } $(,)?) => { ... };
    ($actual:expr, [ $($expected:expr),* ], $($format_args:expr),* $(,)?) => { ... };
    ($actual:expr, { $($expected:expr),* }, $($format_args:expr),* $(,)?) => { ... };
    ($actual:expr, $expected:expr $(,)?) => { ... };
    ($actual:expr, $expected:expr, $($format_args:expr),* $(,)?) => { ... };
}

Matches the given value against the given matcher, panicking if it does not match.

let value = 2;
assert_that!(value, eq(3));  // Fails and panics.

This is analogous to assertions in most Rust test libraries, where a failed assertion causes a panic.

One may optionally add arguments which will be formatted and appended to a failure message. For example:

let value = 2;
let extra_information = "Some additional information";
assert_that!(value, eq(3), "Test failed. Extra information: {extra_information}.");

This is output as follows:

Value of: value
Expected: is equal to 3
Actual: 2,
  which isn't equal to 3
  at ...
Test failed. Extra information: Some additional information.

Note for users of GoogleTest for C++: This differs from the ASSERT_THAT macro in that it panics rather than triggering an early return from the invoking function. To get behaviour equivalent to ASSERT_THAT, use verify_that! with the ? operator.