How to test if no event was invoked

I am new to UnitTests and therefore to Xunit. I have wrote some tests, but I am stuck with the testing of events.

Is it possible to test that no event was invoked with xunit?

I used this example for preparing my tests.

The first test works fine. For the second test, I expected something like 'Assert.RaisesNoEvent'; However, that method is not available.

Is there another way to test that no event was invoked?

Class where Event is Raised when Property2 is Set

Class

Property2

Set

public class Class

private int _property2;

public event EventHandler RelevantPropertyChanged;
public void OnRelevantPropertyChanged(EventArgs args)
RelevantPropertyChanged?.Invoke(this, args);


public int Property1 get; set;
public int Property2
get return _property2;
set
OnRelevantPropertyChanged(new EventArgs());
_property2 = value;





TestClass defines unit tests for Class

TestClass

Class

public class TestClass


[Fact]
public void ChangeProperty2_RaisesEvent()

var cl = new Class();
var args = new EventArgs();

var evt = Assert.RaisesAny<EventArgs>(
h => cl.RelevantPropertyChanged += h,
h => cl.RelevantPropertyChanged -= h,
() => cl.Property2 = 5);

Assert.NotNull(evt);
Assert.Equal(cl, evt.Sender);
Assert.Equal(args, evt.Arguments);


[Fact]
public void ChangeProperty1_RaisesNoEvent()

var cl = new Class();
Action code = () => cl.Property1 = 5;

Assert.RaisesNoEvent(code); //this is what I want to do




1 Answer
1

You can check that the event was not raised by checking that the EventHandler was not invoked:

[Fact]
public void ChangeProperty1_RaisesNoEvent()

var instance = new Class();
bool isInvoked = false;
instance.RelevantPropertyChanged += (s, e) => isInvoked = true;

Assert.False(isInvoked);
instance.Property1 = 5;
Assert.False(isInvoked);



This technique works with any unit testing framework.

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