JavaScript Testing with Jasmine

Chapter 1. Intro to Testing

What Is Software Testing?

In short, you can test software against a specification.

Let’s say you’re writing a simple calculator that just does addition. Before you even start, think about how it should behave. It should be able to add positive integers. It should be able to add negative integers. It should be able to add decimal numbers, not just integers. You can think of many different ways that your calculator needs to work.

Before you’ve written any of the code, you know how you want it to behave. You have a specification for its behavior.

You can write these specifications in code. You’d say, “OK, it should work this way.” You’d make tests that added 1 and 1, 2 and 2, –1 and 5, –1.2 and 6.8, 0 and 0, and so on. When you run these tests, you’ll either get a success (it works according to the specification) or a failure (it doesn’t). If you ran all of your tests and saw success for each, then you can be pretty sure that your calculator works. If you ran these tests and saw some failures, then you know that your calculator doesn’t work.

That’s software testing in a nutshell. You’re testing your code against a specification. There are many tools (Jasmine among them) that help you automate these software tests.

It’s important to know that it’s difficult (and often impossible) to write tests for every case. In the calculator example, there are an infinite number of possible combinations. When testing, you should try to cover every reasonable case by testing ...