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Simple test

Contents

In this chapter, you’ll add code, and test it with Jest.

How it works

  • Test files import from sources and defines test cases with assertions.

  • Test files written for Jest uses describe and (test/it) functions to organize the test cases.

  • The expect function is used to write assertions and returns an object which contains a bunch of Jest matchers.

  • The test below uses the toEqual matcher, see https://jestjs.io/docs/using-matchers for more matchers.

Source code

Add the source file to your project:

src/main/resources/lib/myproject/fibonacci.ts 
export function fibonacci(n: number): number[] {
    const fib = [0, 1];
    for (let i = fib.length; i < n; i++) {
        fib[i] = fib[i - 2] + fib[i - 1];
    }

    return fib;
}
Source code should (as always) be placed within the /src/main/resources section of your project

The test

Now, add your test file:

src/jest/server/fibonacci.test.ts 
import {
    describe,
    expect,
    test as it
} from '@jest/globals';
import { fibonacci } from '/lib/myproject/fibonacci';


describe('fibonacci', () => {
    it('should return the first 10 numbers in the fibonacci sequence', () => {
        expect(fibonacci(10)).toEqual([0, 1, 1, 2, 3, 5, 8, 13, 21, 34]);
    });
});
By default, your tests should be placed in /src/jest.

Execution

Run the tests:

npm run cov src/jest/server/fibonacci.test.ts

This should produce an output looking something like this:

> tutorial-jest@1.0.0 test
> jest --no-cache --coverage src/jest/server/fibonacci.test.ts

 PASS   SERVER  src/jest/server/fibonacci.test.ts
  fibonacci
    ✓ should return the first 10 numbers in the fibonacci sequence (3 ms)

--------------|---------|----------|---------|---------|-------------------
File          | % Stmts | % Branch | % Funcs | % Lines | Uncovered Line #s
--------------|---------|----------|---------|---------|-------------------
All files     |     100 |      100 |     100 |     100 |
 fibonacci.ts |     100 |      100 |     100 |     100 |
--------------|---------|----------|---------|---------|-------------------
Test Suites: 1 passed, 1 total
Tests:       1 passed, 1 total
Snapshots:   0 total
Time:        1.029 s
Ran all test suites matching /src\/jest\/server\/fibonacci.test.ts/i.

Summary

This chapter explained how to write and run a simple Jest test for an Enonic XP project.

In order to write more advanced tests, we must introduce a new concept. Let’s have a look at mocking.

Contents

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