Delve into front-end testing principles, learn best practices for writing enduring tests, and discover strategies for E2E testing and integration into CI pipelines. Gain actionable testing insights.

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This course will provide you with important information, principles, and experience-based advice, to enter the world of testing methodologies. 

Here, you will learn the best practices to follow to write useful and lasting tests, how to test different user flows without a working back-end, how to write effective end-to-end tests (E2E), and how to integrate tests into development and Continuous Integration pipelines.

At the end of the course, you will be able to apply the fundamental principles of the test methodologies to understand what and how to test effectively.

Front-end Testing 101: Integration and End-to-end Testing

## Why write low-level tests?
E2E tests and UI integration tests give us high confidence about the whole application, so why should we write low-level tests? 



### Reasons
There are a couple of reasons:
- UI Integration Tests are fast but Cypress generally is not if you need to run all the tests simultaneously.

- High-level tests can tell you what did not work but cannot tell you why. 

- Rendering the entire application is not always the best way to test something as many parts of the application are not related to the render phase at all.

- While the end-user is the most important user of an application, all the components and the functions are also consumed by the developer. Every unit of the project has some APIs (contracts), and they need to be tested too. Testing an end-user flow does not allow you to replicate all the API cases.

- Everything is integrated to compose the final application, but you need to test smaller integrations to earn the confidence you need.

These reasons all depend on project size. A landing page would not need hundreds of different tests, but a standard-sized application would.

# Why write low-level tests?
E2E tests and UI integration tests give us high confidence about the whole application, so why should we write low-level tests? 



## Reasons
There are a couple of reasons:
- UI Integration Tests are fast but Cypress generally is not if you need to run all the tests simultaneously.

- High-level tests can tell you what did not work but cannot tell you why. 

- Rendering the entire application is not always the best way to test something as many parts of the application are not related to the render phase at all.

- While the end-user is the most important user of an application, all the components and the functions are also consumed by the developer. Every unit of the project has some APIs (contracts), and they need to be tested too. Testing an end-user flow does not allow you to replicate all the API cases.

- Everything is integrated to compose the final application, but you need to test smaller integrations to earn the confidence you need.

These reasons all depend on project size. A landing page would not need hundreds of different tests, but a standard-sized application would.

Let's learn why E2E testing is not enough.

Introduction

E2E Testing

The First E2E Test

Polishing the E2E test

Ajax Requests

Custom Commands

UI Integration Tests

Other Best Practices

Bonus Section

Conclusion

Appendix

Why Is E2E Testing Not Enough?

Why write low-level tests?

Reasons