ICommandWrapper Interface

In NUnit 3, test execution is done using command objects, which are constructed for each test. Execution of a single test will generally require multiple nested commands. Some attributes are able to contribute to the chain of commands. For example, MaxTimeAttribute adds a command, which examines the elapsed time to complete a test and fails it if a specified maximum was exceeded.

Attributes add to the command chain by and implementing the two interfaces that derive from the ICommandWrapper interface. The interfaces are defined as follows:

public interface ICommandWrapper
{
    TestCommand Wrap(TestCommand command);
}

public interface IWrapTestMethod : ICommandWrapper
{
}

public interface IWrapSetUpTearDown : ICommandWrapper
{
}

Attributes should not implement the ICommandWrapper interface directly but should select one of the derived attributes. NUnit applies the IWrapSetUpTearDown interface before SetUp and after TearDown. It applies the IWrapTestMethod interface after SetUp and before the test is run.

The Wrap should return an appropriate command in which the original command has been nested. For an example, see the implementation of MaxTimeAttribute.