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Callbacks

Describes the possible expectations for working with callbacks.

Signaler​

First, you have to start recording callback signals using the Signaler class. This class is available in the " aweXpect.Signaling" namespace.

// ↓ Counts signals from callbacks without parameters
Signaler signaler = new();
Signaler<string> signaler = new();
// ↑ Counts signals from callbacks with a string parameter

Then, you can signal the callback on the recording.

class MyClass
{
  public void Execute(Action<string> onCompleted)
  {
    // do something in a background thread and then call the onCompleted callback
  }
}

sut.Execute(v => signaler.Signal(v));

At last, you can wait for the callback to be signaled:

await Expect.That(signaler).Signaled();

You can also verify that the callback will not be signaled:

await Expect.That(signaler).DidNotSignal();

NOTE: The last statement will result never return, unless a timeout or cancellation is specified. Therefore, when nothing is specified, a default timeout of 30 seconds is applied!

Timeout​

You can specify a timeout, how long you want to wait for the callback to be signaled:

await Expect.That(signaler).Signaled().Within(TimeSpan.FromSeconds(5))
  .Because("it should take at most 5 seconds to complete");

Alternatively you can also use a CancellationToken for a timeout:

CancellationToken cancellationToken = new CancellationTokenSource(5000).Token;
await Expect.That(signaler).Signaled().WithCancellation(cancellationToken)
  .Because("it should be completed, before the cancellationToken is cancelled");

Amount​

You can specify a number of times, that a callback must at least be signaled:

await Expect.That(signaler).Signaled(3.Times());

You can also verify that the callback was not signaled at least the given number of times:

await Expect.That(signaler).DidNotSignal(3.Times());

Parameters​

You can also include a parameter during signaling:

Signaler<string> signaler = new();

signaler.Signal("foo");
signaler.Signal("bar");

await Expect.That(signaler).Signaled(2.Times());

You can filter for signals with specific parameters by providing a predicate:

Signaler<string> signaler = new();

signaler.Signal("foo");
signaler.Signal("bar");
signaler.Signal("foo");

await Expect.That(signaler).Signaled(2.Times()).With(p => p == "foo");

In case of a failed expectation, the recorded parameters will be displayed in the error message.