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September 15, 2023

Jest Fundamentals in TS

nodejs

test

Contents

Installation

yarn add jest typescript ts-jest @types/jest
yarn ts-jest config:init

At package.json, add

{
  "script": {
    "test": "env-cmd -f .env-cmdrc -e default,dev jest --coverage"
  }
}

This will debug all the file that bare the name as suffix: .test.ts.

Debug a Single Jest File

Let's define the following in .vscode/launch.json

{
  "version": "0.2.0",
  "configurations": [
    ...,
    {
      "type": "node-terminal",
      "request": "launch",
      "name": "Jest: Current File",
      "command": "yarn env-cmd -f .env-cmdrc -e default,dev jest ${fileBasenameNoExtension} --config jest.config.js --coverage",
      "cwd": "${workspaceRoot}",
    }
  ]
}

Now go to the file we want to debug, press F5.

Examples of Test Files

Expect an Output is as Expected

Let's consider testing an API to create a document:

import getMongoConnection from "../src/db/getMongoConnection";
import { NameSpaceModel } from "../src/db/models/NameSpace";

test("Create Namespaces", async () => {
  await getMongoConnection();
  const namespaceDoc = await new NameSpaceModel({
    name: "wonderbricks",
    path: "/wonderbricks",
  }).save();

  expect(
    namespaceDoc.name === "wonderbricks" &&
      namespaceDoc.path === "/wonderbricks"
  ).toBe(true);
});

And we get

$ C:\Users\user\Repos\wonderbricks\2023-09-12-serverless-chat-billie\node_modules\.bin\env-cmd -f .env-cmdrc -e default,dev jest new-namspace.test --config jest.config.js --coverage
Debugger attached.
Debugger attached.
  console.log
    Connecting to mongo ...

      at log (src/db/getMongoConnection.ts:8:13)

  console.log
    Mongo connected.

      at log (src/db/getMongoConnection.ts:13:17)

 PASS  test/new-namspace.test.ts (5.286 s)
  √ Create Unique Namespaces (2858 ms)

------------------------|---------|----------|---------|---------|-------------------
File                    | % Stmts | % Branch | % Funcs | % Lines | Uncovered Line #s
------------------------|---------|----------|---------|---------|-------------------
All files               |   93.33 |    33.33 |     100 |   92.85 |
 db                     |   91.66 |    33.33 |     100 |    90.9 |
  getMongoConnection.ts |   91.66 |    33.33 |     100 |    90.9 | 10
 db/models              |     100 |      100 |     100 |     100 |
  NameSpace.ts          |     100 |      100 |     100 |     100 |
------------------------|---------|----------|---------|---------|-------------------
Test Suites: 1 passed, 1 total
Tests:       1 passed, 1 total
Snapshots:   0 total
Time:        5.449 s, estimated 8 s
Ran all test suites matching /new-namspace.test/i.
Expect an Async Function not to Throw Error
test("Create Unique Namespaces", async () => {
  const createNamespace = async () => {
    await getMongoConnection();
    await new NameSpaceModel({
      name: "jamesCompany",
      path: "/jamesCompany",
    }).save();
  };
  await expect(createNamespace()).resolves.not.toThrowError();
});