go-stack-2019

Testing Node Applications

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Types of testings

Unit tests

It tests a pure and minimum function, which does not perform side effects such as DB accessing or external integrations;

Integration testings

It is the main est for back-end. It tests complete functionalities such as routes till the controller return. (mocks = fakes functionalities)

E3E testings

Testing of interfaces which simulates the user (generally for front-end). It tests the flow of application.

TDD - Test Driven Development

• It creates tests before the functionalities (it is kind a to-do list for the development);
• It facilitates the visualiation of the business rules;
• The process of this kind of development is based on three steps: RED ➡ GREEN ➡ REFACTOR

1. Red: It means the implementation of tests however it will not pass because we don’t have the functionality yet;
2. Green: Our goal is to develop the functionality not worrying about the code quality, but only to pass the test implemented at the first/red step;
3. Refactor: Finally we will take care of the quality of the code in order to improving it.

Jest

• It can be implemented in Node / React / React Native’s apps;
• It is a testing framework from Facebook;
• Code Coverage integrated;
• Multi-thread integrated (uses more than 1 thread from processor improving the spped of tests);

Configuring the project

Using @rocketseat/omni for project creation

In order to automate the process of creating a new Node’s project, we will use a lib which is a CLI that creates projects (Node/React/ReactNative) based on the resources which we hav implemented before.

yarn global add @rocketseat/omni

For new project: omni init projectName --onlyserver (--onlyserver will create a Node project. If you do not put anything, it will create a Node/React/ReactNative project at once).

Configuring JEST

Install it yarn add jest -D, afterwards run yarn jest --init and answer the following questions:

It has created jest.config.js and let’s make some changes:

1. bail: 1 (if have some error in a tet, it will stop immediately);
2. collectCoverage: true;
3. collectCoverageFrom: ['src/app/**/*.js'] (where are the codes swhich will be tested. It is not necessary another files such as app.js, routes.js and server.js. ** means every folder);
4. coverageReporters: [ "text","lcov"],; 5.

testMatch: [
    "**/__tests__/**/*.test.js",
  ],

(the place which the script tests will be stored. In this case the script tests will be stored at /__tests__/ and the suffix name will be <something>.test.js);

By default, Jest will perform it tests using commonJS scripts, like require(), and not import {} from '' that we are using till now. To fix this, we can install a functionality from sucrase: yarn add @sucrase/jest-plugin -D. And within jest.config.js replace transform to the following code:

transform: {
  ".(js|jsx|ts|tsx)": "@sucrase/jest-plugin"
},

Finally, we will open nodemon.js and add the following line in order to Nodemon not reload the application every time we change some script test in __tests__ folder:

{
  "execMap": {
    "js": "sucrase-node"
  },
  "ignore": ["__tests__"]
}

Creating first test code

Before create our first test script, let’s install a dependency which will make the Intellisense to show the codes: yarn add -D @types/jest.

Within __tests__ folder, let’s create example.test.js.

Test() function

This command will indicate whether some function passes the test:

// let's test the follow function
function sum(a, b) {
  return a + b;
}

test("if I call sum() function with 4 and 5 it should return 9", () => {
  const result = sum(4, 5);

  expect(result).toBe(8); // testing if expected result will be 9
});

Running yarn test it will execute each test within __tests__ folder and will return the results.

After running the tests, it will be created coverage folder, which is an user-friendly interface from coverage test. Let’s configure jest.config.js at the following line code to create this folder in __tests__ folder:

coverageDirectory: "__tests__/coverage";