public void should_return_true_on_nonempty_trypeek(IPeekable <string> subject, string expected)
{
string value;
subject.TryPeek(out value).Should().BeTrue();
value.Should().Be(expected);
}
public void should_return_false_on_empty_trypeek(IPeekable <int> subject)
{
int value;
subject.TryPeek(out value).Should().Be(false);
}