Test guide – we drive the design

In Chapter 5, Writing Our First Test, we wrote our first test. To do that, we ran through a number of design decisions. Let’s review that initial test code and list all the design decisions we had to make, as follows:

@Test
public void oneIncorrectLetter() {
    var word = new Word("A");
    var score = word.guess("Z");
    assertThat( score.letter(0) ).isEqualTo(Letter.INCORRECT);
}

We decided on the following:

• What to test
• What to call the test
• What to call the method under test
• Which class to put that method on
• The signature of that method
• The constructor signature of the class
• Which other objects should collaborate
• The method signatures involved in that collaboration
• What form the output of this method will take
• How to access that output and assert that it worked

These are all design decisions that...