• Getting started
• Creating a substitute
• Setting a return value
• Return for specific args
• Return for any args
• Return from a function
• Multiple return values
• Replacing return values
• Checking received calls
• Clearing received calls
• Argument matchers
• Callbacks, void calls and When..Do
• Throwing exceptions
• Safe configuration and overlapping calls
• Raising events
• Auto and recursive mocks
• Setting out and ref args
• Actions with argument matchers
• Checking call order
• Partial subs and test spies
• Return for all calls of a type
• Threading
• Compatibility argument matchers
• NSubstitute.Analyzers
• How NSubstitute works
• Search

Clearing received calls

A substitute can forget all the calls previously made to it using the ClearReceivedCalls() extension method.

Say we have an ICommand interface, and we want a OnceOffCommandRunner that will take an ICommand and only run it once.

public interface ICommand {
    void Execute();
}

public class OnceOffCommandRunner {
    ICommand command;
    public OnceOffCommandRunner(ICommand command) {
        this.command = command;
    }
    public void Run() {
        if (command == null) return;
        command.Execute();
        command = null;
    }
}

If we substitute for ICommand we can test it is called on the first run, then forget any previous calls made to it, and make sure it is not called again.

var command = Substitute.For<ICommand>();
var runner = new OnceOffCommandRunner(command);

//First run
runner.Run();
command.Received().Execute();

//Forget previous calls to command
command.ClearReceivedCalls();

//Second run
runner.Run();
command.DidNotReceive().Execute();

ClearReceivedCalls() will not clear any results set up for the substitute using Returns(). If we need to this, we can replace previously specified results by calling Returns() again.