Macro frame_support::testing_prelude::assert_noop

macro_rules! assert_noop {
    (
		$x:expr,
		$y:expr $(,)?
	) => { ... };
}

Evaluate an expression, assert it returns an expected Err value and that runtime storage has not been mutated (i.e. expression is a no-operation).

Used as assert_noop(expression_to_assert, expected_error_expression).