Deliberate Practice In Tests

Something else we touched on in “Being a Better Developer” are the benefits of deliberate practice.

Over the years I’ve developed a habit I’d consider deliberate practice, and that’s the habit of writing unit tests when learning a new language, framework, or library. I’m not testing for quality, but trying to internalize what I’m learning about a new topic by writing code and experimenting.

Learning becomes a combination of reading documentation, reading source code (sometimes via a decompiler), and practicing code by writing code in tests.

For example, here are some of the tests I’ve written again the new Immutable Collections:

[Fact]
public void Modification_Returns_A_New_List()
{
    var list1 = ImmutableList.Create<int>(1);
    var list2 = list1.Add(2);

    Assert.False(Object.ReferenceEquals(list1, list2));
}

[Fact]
public void Create_Always_Returns_Same_Empty_List()
{
    var list1 = ImmutableList.Create<int>();
    var list2 = ImmutableList.Create<int>();

    Assert.True(Object.ReferenceEquals(list1, list2));
}

[Fact]
public void Clear_Returns_Same_Empty_List_As_Create()
{
    var list1 = ImmutableList.Create<int>(1,2,3);
    var list2 = ImmutableList.Create<int>();

    list1 = list1.Clear();

    Assert.True(Object.ReferenceEquals(list1, list2));
}

Writing simple tests like these give me confidence in using a new technology.