Assertions are central to unit testing in any of the xUnit frameworks, and NUnit is no exception. NUnit provides a rich set of assertions as static methods of the Assert class.
If an assertion fails, the method call does not return and an error is reported. If a test contains multiple assertions, any that follow the one that failed will not be executed. For this reason, it's usually best to try for one assertion per test.
Each method may be called without a message, with a simple text message or with a message and arguments. In the last case the message is formatted using the provided text and arguments.
For convenience of presentation, we list the available assertions in three groups: comparisons, single condition tests and utility methods.