/// <summary>
/// Asserts that the current <see cref="Task{T}"/> will complete within the specified time.
/// </summary>
/// <param name="timeSpan">The allowed time span for the operation.</param>
/// <param name="because">
/// A formatted phrase as is supported by <see cref="string.Format(string,object[])" /> explaining why the assertion
/// is needed. If the phrase does not start with the word <i>because</i>, it is prepended automatically.
/// </param>
/// <param name="becauseArgs">
/// Zero or more objects to format using the placeholders in <see cref="because" />.
/// </param>
public async Task <AndWhichConstraint <AsyncFunctionAssertions, Task> > CompleteWithinAsync(
TimeSpan timeSpan, string because = "", params object[] becauseArgs)
{
var timeoutCancellationTokenSource = new CancellationTokenSource();
Task task = Subject();
Task completedTask =
await Task.WhenAny(task, timer.DelayAsync(timeSpan, timeoutCancellationTokenSource.Token));
if (completedTask == task)
{
timeoutCancellationTokenSource.Cancel();
await completedTask;
}
Execute.Assertion
.ForCondition(completedTask == task)
.BecauseOf(because, becauseArgs)
.FailWith("Expected {context:task} to complete within {0}{reason}.", timeSpan);
return(new AndWhichConstraint <AsyncFunctionAssertions, Task>(this, task));
}