Desired Test Declaration

If we’re going to have a test-driven development (TDD) process, we need tests. This chapter will explain what the tests will do, how we will write them, and how we will use them.

We’ll be starting from the very beginning and slowly building a full library to help manage and run tests, and we’ll be using the test library to help build itself. Initially, there will only be a single test. The following chapters will add more capabilities and grow the test library.

Starting with the end goal in mind, we’ll first think about what it will be like to create and use a test. Writing tests is a big part of TDD, so it makes sense to start thinking about testing even before we have the ability to create and run tests.

TDD is a process that will help you design better code and then make changes to your code without breaking parts that you’ve already verified to be working as expected. In order for this process to work, we need to be able to write tests. This chapter will explore what tests can do for us and how we can write them.

We’ll cover the following main topics in this chapter:

• What do we want tests to do for us?
• What should a test look like?
• What information does a test need?
• How can we use C++ to write tests?
• How will the first test be used?