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https://github.com/aldenvallestero/serverless-unit-test-boilerplate

This repository is created to help beginners understand the basic, fast and easy way to score almost 100% of unit test coverage using the serverless framework.
https://github.com/aldenvallestero/serverless-unit-test-boilerplate

javascript jest nodejs serverless unit-testing

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This repository is created to help beginners understand the basic, fast and easy way to score almost 100% of unit test coverage using the serverless framework.

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# serverless-unit-test-boilerplate

This repository is created to help beginners understand the fast and easy way to score almost 100% of unit test coverage using the serverless framework. The code demonstrates how to send either SMS or Email Notification using Axios to call the service provider and Jest for testing.



This will also help you prevent pipeline execution errors due to unavailable dependencies within its environment such as, cloud resources, API calls and database connectivity.



## 🧱 System Architecture

![System Architecture](graphics/system-architecture-graphic.png)



## 🧪 Test Coverage Result

![Test Coverage Result](graphics/test-coverage-graphic.png)



## 💡 General Idea

To ensure comprehensive unit test coverage while maintaining organized test files, focus exclusively on the handler files. By simulating a serverless event through mocking, you can establish a straightforward framework for unit testing. This approach facilitates the creation of additional test cases, encompassing middleware handling, error capture, and various aspects within the deeper service layers as you expand your coverage.



![System Architecture](graphics/test-cases-graphic.png)



## 👣 Steps to take

1. Clone and try the boilerplate to fully understand the steps in unit testing the handler layer. Make sure that you have a good understanding in serverless and jest library so it would be more easier to follow the instructions.

2. Implement it to your own project by create an event generator file first which represents an https request when calling your handlers.

3. Create a fixutre file (Not included in the reposotory yet!) which contains the payload that is going to be the value being passed to the event generator.

4. Create test files and follow the index test file given here, add your event generator and payload for each test case.

5. Combine event generator and sample payloads / fixtures & call the handler file.



### 🤝 Dealing with 3rd Party APIs

To prevent slow, delayed and possible runtime error in your CI/CD pipeline, make sure to mock every possible 3rd Part API call responses for each test cases based on the expected result you want to have.



```

const axios = require('axios');

const mockServerlessEvents = require('./event-generator');

const { sendSMSNotification, sendEmailNotification } = require('./handler');



jest.mock('axios');



describe('Notification Service Unit Test', () => {

  beforeEach(() => {

      jest.clearAllMocks();

  });



  test('Should SUCCEED delivering SMS notification', async () => {

    axios.mockResolvedValue({ status: 200 })

    const event = mockServerlessEvents({ body: { message: 'Hello World!' } });

    const result = await sendSMSNotification(event);

    expect(result.statusCode).toBe(200);

  });

```



From the image above, you will see that before the execution of this test file, axios is expected to return mock responses based on its configuration for each test cases.



```jest.mock('axios');```

```axios.mockResolvedValue({ status: 200 });```



Notice the sequence of test case above:

1. Mock 3rd Party API that uses Axios.

2. Set payload for mocked serverless event using the event generator. It consist of body, headers, path parameters, and query string parameters similar to what HTTP request payload.

3. Perform the unit testing directly hitting the handlers layer.

4. Expect the result.



It's that simple!



This skip the unnecessary business logic and focuses only on the unit testing and making sure that the legacy code is working properly and prevents potential bugs in the first place.



A friendly reminder, don't forget to clear your axios mocks before moving to another test case, the image below shows you how to clear previous mock.



```

beforeEach(() => {

  jest.clearAllMocks();

})

```



### ❓ FAQs

**Where's the database explanation & why is it not included in the repository?**

Due to short amount of time I allocated to this repository, I will be preparing another push to this public repository ASAP.



### 📋 Todo

- [ ] Create a fixture sample.

- [ ] Create a database connectivity sample.