public void TestFireOnce()
{
int ea = 0;
EventHandler <EventArgs> eventWithArgs = (sender, args) => ea++;
Delegates.AttachWithUnsubscribe(this, nameof(DelegateTests.TestEventArgs), eventWithArgs);
TestEventArgs?.Invoke(this, null);
TestEventArgs?.Invoke(this, null);
TestEventArgs?.Invoke(this, null);
ea.ShouldBeEquivalentTo(1);
TestEventArgs.Should().BeNull();
}