README.md

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In this lesson, we will learn, how to test the web endpoints of our application. But before doing that, make sure you have configured the pre-commit hook to run tests and lint-staged using husky.

To run the tests, we use jest. Along with jest, we will also install another npm package called supertest. We will use supertest to send request to our express.js routes.

npm install -D jest supertest

Next, we will edit the test scripts in package.json to drop and create the database before running the tests. We will use the db:drop command available with sequelize-cli to destroy the test database. Then we create a clean slate by using the db:create command.

"pretest": "NODE_ENV=test npx sequelize-cli db:drop && NODE_ENV=test npx sequelize-cli db:create",
"test": "NODE_ENV=test jest --detectOpenHandles"

Next, let's make sure we have correct parameters to connect to database in config/config.json. We will also use a separate database for testing.

{
  "development": {
    "username": "postgres",
    "password": "postgres",
    "database": "wd-todo-dev",
    "host": "127.0.0.1",
    "dialect": "postgres"
  },
  "test": {
    "username": "postgres",
    "password": "postgres",
    "database": "wd-todo-test",
    "host": "127.0.0.1",
    "dialect": "postgres",
    "logging": false
  },
  "production": {
    "username": "root",
    "password": null,
    "database": "database_production",
    "host": "127.0.0.1",
    "dialect": "mysql"
  }
}

And finally, let's make sure jest is installed in our project. Make sure you have configured pre-commit hook to run the tests and lint staged as we learned in Level 4.

Now let's start writing some tests!

Test listing of todos

To make our code testable, we will rename our index.js to app.js. And export the file as a module. We will also remove the app.listen from the file.

app.delete("/todos/:id", (request, response) => {
  console.log("Delete a todo by ID: ", request.params.id)
})


module.exports = app;

Create a new index.js file with following content:

//  index.js
const app = require("./app");

app.listen(3000, () => {
  console.log("Started express server at port 3000")
})

Create a folder __tests__ in the project root and create a file named todos.js. We make sure the tables are created before running the tests using the beforeAll global function available with jest. We also tear down the temporary server once testing is complete using the afterAll global function.

We will now test creating a new todo.

With the test, we make sure:

• The endpoint is available
• Returns a JSON response
• The response contains id of newly created todo.

const request = require("supertest");

const db = require("../models/index");
const app = require("../app");

let server, agent;

describe("List the todo items", function () {
  beforeAll(async () => {
    await db.sequelize.sync({ force: true });
    server = app.listen(3000, () => { });
    agent = request.agent(server);
  });

  afterAll(async () => {
    await db.sequelize.close();
    server.close()
  })

  test("responds with json at /todos", async () => {
    const response = await agent.post('/todos').send({
      'title': 'Buy milk',
      dueDate: new Date().toISOString(),
      completed: false
    });
    expect(response.statusCode).toBe(200);
    expect(response.header["content-type"]).toBe(
      "application/json; charset=utf-8"
    );
    const parsedResponse = JSON.parse(response.text);
    expect(parsedResponse.id).toBeDefined();
  });
});

Run the tests using the command npm test. You should see the tests running and something similar to the following as output.

> [email protected] test
> NODE_ENV=test jest --detectOpenHandles

  console.log
    Creating a todo {
      title: 'Buy milk',
      dueDate: '2022-09-20T19:23:20.961Z',
      complete: false
    }

      at log (app.js:13:11)

 PASS  __tests__/todo.js
  List the todo items
    ✓ create a new todo (83 ms)

Test Suites: 1 passed, 1 total
Tests:       1 passed, 1 total
Snapshots:   0 total
Time:        1.079 s, estimated 2 s
Ran all test suites.

We have successfully added test for creating todo items. Next, let's add test to check the mark complete functionality.

test("Mark a todo as complete", async () => {
    const response = await agent.post('/todos').send({
      'title': 'Buy milk',
      dueDate: new Date().toISOString(),
      completed: false
    });
    const parsedResponse = JSON.parse(response.text);
    const todoID = parsedResponse.id;

    expect(parsedResponse.completed).toBe(false);

    const markCompleteResponse = await agent.put(`/todos/${todoID}/markASCompleted`).send();
    const parsedUpdateResponse = JSON.parse(markCompleteResponse.text);
    expect(parsedUpdateResponse.completed).toBe(true);
  });

Let's run the tests again.

npm test

You should be able to see the following output.

 PASS  __tests__/todo.js
  List the todo items
    ✓ create a new todo (87 ms)
    ✓ Mark a todo as complete (46 ms)

Test Suites: 1 passed, 1 total
Tests:       2 passed, 2 total
Snapshots:   0 total
Time:        1.113 s, estimated 2 s
Ran all test suites.

Conclusion

You have now added tests to back your code. This would ensure the code will work as it is intended.