public void CanPeekOrElseEmpty_PeekOrElse_Test()
{
// Arrange
var stack = new CheckedLayeredStack <string>();
var arbitrary = "foobar";
// Act
var x = stack.PeekOrElse(orElse: arbitrary);
var y = stack.PeekItemOrElse(0, orElse: arbitrary);
// Assert
Assert.Equal(arbitrary, x);
Assert.Equal(arbitrary, y);
}