Mastering Rust - Second Edition

Assertion macros

In testing, when given a test case, we try to assert the expected behavior of our software component on a given range of inputs. Languages usually provide functions called assertion functions to perform these assertions. Rust provides us with assertion functions, implemented as macros, that help us achieve the same thing. Let's take a look at some of the commonly used ones:

      assert!(true);      assert!(a == b, "{} was not equal to {}", a, b);

• assert!: This is the simplest assertion macro that takes a Boolean value to assert against. If the value is false, the test panics, showing the line where the failure happened. This can additionally take in a format string, followed by a corresponding number of variables, for providing custom ...