Code Recipe: GameTime

Dealing with time in Unity isn't really painful, there is a convenient Time static object that unity provides which has a bunch of properties that track the passage of time in your game.

It only becomes painful once you begin to test code that uses that Time object. Since it's a static object it's almost impossible to mock. The solution I've used for a while is to create a GameTime class that wraps Unitys Time object and use that instead.

It's easy enough and doesn't add that much overhead, plus since it implements an interface it's very easy to mock out.

public interface IGameTime {
    float deltaTime { get; }
    float fixedDeltaTime { get; }
    int frameCount { get; }
    float time { get; }
    float realtimeSinceStartup { get; }
}

public class GameTime : IGameTime {
    public float deltaTime => Time.deltaTime;

    public float fixedDeltaTime => Time.fixedDeltaTime;

    public int frameCount => Time.frameCount;
    public float time => Time.time;

    public float realtimeSinceStartup => Time.realtimeSinceStartup;
}

Putting it to use is really simple:

public SomeConstructor(IGameTime time = null) {
    _time = time ?? new GameTime();
    _startTime = _time.realtimeSinceStartup;
}

And mocking time in unit tests becomes trivial:

var mockTime = new Mock<IGameTime>(MockBehavior.Strict);
mockTime.Setup(m => m.deltaTime).Returns(1000f/60f);

var myObject = new SomeConstructor(mockTime.Object);

// write the rest of your test.

What do you think? Shoot me your thoughts on twitter.