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 = 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

//Forget previous calls to command

//Second run

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.