10.1.4: Set Up the Testing Framework: Bootcamp: UNC-VIRT-BO-FSF-PT-12-2021-U-B-TTH

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• Now that we've set up the basic structure for our project, we can start setting up the testing framework

• Before we do that, let's pause to examine test-driven development (TDD) in more detail.

• TDD is a software development practice in which a developer creates failing test cases, and then writes code so that the tests pass.

• Red, Green, Refactor.

• It's important to note that TDD isn't simply about adding tests. It encompasses the process of writing tests before you write a single line of code, and then writing code in small increments.

• We'll use the Jest framework for the tests we writ

• First, run npm install jest --save-dev. The --save-dev flag tells npm to add Jest to the devDependencies list.

• . If we already had a package.json file with both dependencies and devDependencies properties, running npm install would install all packages from both lists.

• npm scripts allow us to add short snippets that we want our project to run at different stages during the build that we would otherwise run from the command line.

• All other scripts must follow the convention: npm run <scriptname>. For more details, visit the npm docs (Links to an external site.).

• Technically, you could—but adding scripts to package.json allows other developers to join the project without needing to know exactly which commands are run to build and test the application.

• We separate all our tests into their own folder so that we can clearly differentiate between the application code and testing code.

• Let's create our first test! We'll start with a simple one.

• In the __tests__ directory, create a new file named random.test.js. We use the *.test.js naming convention because this is what Jest expects. This also helps us keep things organized, since our test file has a different name than our constructor file

• Did you notice that the test reads almost like plain English?

• it should be very clear to anyone what the test is checking for and whether it passed

• Right now, our test doesn't pass. If you run the test with the command npm run test, it will fail, due to checkIfEqual() not being a function. This is expected because the file random.js doesn't exist yet.

• random.test.js.

• We still need to add a line to lib/random.js so that checkIfEqual refers to a module.

• There's still one more step in TDD—the refactor step. This one leaves the most room for interpretation.