用发电机对工厂进行单元测试

Question

I have a Factory class that uses a Generator class (there will be several of these, each with a different algorithm) to produce arrays of objects. I am trying to program this with a TDD approach, but I'm having great difficulty with deciding on tests. I've barely just started with TDD, so I guess that my tests are, in fact, ugly abominations.

These are the tests I have on the Factory :

[TestFixture]
public class MapRegionFactoryTests
{
    [Test,
     Description("Tests if a MapRegion is successfully created.")]
    public void TestBasicRegionCreation()
    {
        var mapRegionFactory = new MapRegionFactory();
        MapRegion mapRegion = mapRegionFactory.GenerateMapRegion();

        Assert.IsTrue(mapRegion != null);
    }

    [Test,
     Description("Tests if a MapRegionFactory's RegionSizeX, RegionSizeY and RegionSizeZ are properly initialized" +
                 "to their default values.")]
    public void TestDefaultPropertyInitialization()
    {
        var mapRegionFactory = new MapRegionFactory();

        Assert.Greater(mapRegionFactory.RegionSizeX, 0);
        Assert.Greater(mapRegionFactory.RegionSizeY, 0);
        Assert.Greater(mapRegionFactory.RegionSizeZ, 0);
    }

    [Test,
     Description("Tests if properties can only be assigned numbers above zero.")]
    public void TestGreaterThanZeroPropetyAssignment()
    {
        var mapRegionFactory = new MapRegionFactory
                               {
                                   RegionSizeX = -8,
                                   RegionSizeY = -3,
                                   RegionSizeZ = 0
                               };

        Assert.Greater(mapRegionFactory.RegionSizeX, 0);
        Assert.Greater(mapRegionFactory.RegionSizeY, 0);
        Assert.Greater(mapRegionFactory.RegionSizeZ, 0);
    }

    [Test,
    Description("Tests if the default RegionFactory can deliver a region filled with tiles.")]
    public void TestRegionCount()
    {
        // Test the count of objects again?
    }
}

And a single test for the Generator :

[TestFixture]
public class MapRegionGeneratorTests
{
    [Test,
     Description("Tests that a region of a certain size is properly filled with Block objects.")]
    public void TestDefaultRegionSize()
    {
        const int regionSize = 16;

        var mapRegionGenerator = new MapRegionGenerator();

        var regionData = mapRegionGenerator.GenerateRegion(regionSize);

        foreach (Block element in regionData)
        {
            Assert.IsNotNull(element);
        }
    }
}

Am I approaching this correctly so far? I know that MapRegionFactory will have an IMapRegionGenerator injected through Castle.Windsor, but how do I mock something as complex as a generator? I can't replicate the whole generating code, no?

Answer 1

Why not use constructor injection , ie pass an instance of IMapRegionGenerator type to the constructor of MapRegionFactory class?

class MapRegionFactory
{
    public MapRegionFactory(IMapRegionGenerator generator)
    {
        ...
    }

    ...
}

After this you can create mock for the IMapRegionGenerator type and pass it for testing.

Answer 2

I don't know enough about your code to know exactly how this test should look, but it ought to give you a basic idea of how to test the factory with a mock generator.

[Test]
public void RegionFactoryDelegatesToRegionGenerator()
{
    var mockGenerator = new Mock<IMapRegiongenerator>();
    var factory = new MapRegionFactory(mockGenerator.Object);

    var expectedRegion = new Region();
    var regionSize = CreateRandomRegionSize();
    mockGenerator.Setup(g=>g.GenerateRegion(regionSize)).Returns(expectedRegion);

    factory.SetRegionSize(regionSize);
    Assert.That(factory.GetRegion(), Is.SameAs(expectedRegion));
}

how do I mock something as complex as a generator? I can't replicate the whole generating code, no?

For the purpose of testing the factory, you just have to ensure that it uses the generator correctly, whatever correctly means. Your tests, like your production code for the factory, don't and should not care how a generator works, just that it fulfills its contract and returns a Region.