Package assert implements the same assertions as the `assert` package but stops test execution when a test fails. The following is a complete example using require in a standard test function: The `require` package have same global functions as in the `assert` package, but instead of returning a boolean result they call `t.FailNow()`. Every assertion function also takes an optional string message as the final argument, allowing custom error messages to be appended to the message the assertion method outputs.