public void ShouldCreateJustOneInstance()
{
SingletonClass first = SingletonClass.Instance;
SingletonClass second = SingletonClass.Instance;
this.output.WriteLine($"First instance hashcode: {first.GetHashCode()}");
this.output.WriteLine($"Second instance hashcode: {second.GetHashCode()}");
Assert.Same(first, second);
first.SomeValue++;
this.output.WriteLine($"First instance {nameof(SingletonClass.SomeValue)}: {first.SomeValue}");
this.output.WriteLine($"Second instance {nameof(SingletonClass.SomeValue)}: {second.SomeValue}");
Assert.Equal(first.SomeValue, second.SomeValue);
second.SomeValue++;
this.output.WriteLine($"First instance {nameof(SingletonClass.SomeValue)}: {first.SomeValue}");
this.output.WriteLine($"Second instance {nameof(SingletonClass.SomeValue)}: {second.SomeValue}");
Assert.Equal(first.SomeValue, second.SomeValue);
}