How Synthetic Tests and End-to-End Tests Fit Together

I was introducing you in this post to the concept of synthetic testing and why are synthetic tests so useful.

As a software tester, you may have encountered the term "end-to-end testing" or heard someone mention the need for such tests.

If you're not familiar with end-to-end testing, let me give you a quick summary of what it is and why it's useful to integrate it into your software development delivery process.

End-to-end (or e2e) testing is a software testing methodology that focuses on evaluating the entire flow of an application, from the user's perspective, to ensure that all integrated components work together as intended before it is launched in the market. The purpose of e2e testing is to validate the system's behavior, functionality, and performance across and ensure that the multiple modules or subsystems are working correctly together. This type of testing mimics real-world scenarios and user interactions, checking if the application can handle various inputs and conditions throughout the complete user journey. And very important, to allow developers to fix them before they become a problem for users.

As I explained to you in this post, synthetic tests are used for monitoring the production environment from an end-user perspective and identifying potential problems in your system before real users encounter them. This allows you to quickly find and fix issues on production before they become a problem for your customers.

On the other hand, when you find an issue or a problem that is already in production, even if you discover it before your customers do, it becomes more expensive for your team and your company to fix it. It is more desirable to find the problems in your code before they get into production, as you know that no end-user has been already affected by it.

Another downside of relying only on monitoring the production and in fast interventions to fix the potential problems is that nowadays, the systems that we are building are becoming increasingly complex each day, integrating external systems or external APIs, which of course are way harder to be checked. Also, when the system we are building and testing is integrating external services, it becomes very expensive to spin up some production-like environments for us to be able to monitor them through synthetic tests.

And here comes the importance of this duo, synthetic tests and end-to-end tests.

By implementing both types of tests in your software development process:

👉 Your feedback loop gets more complex

Synthetic tests, being more focused, provide quick feedback on the performance and functionality of specific components, while end-to-end tests provide a more comprehensive validation of the application's end-user experience and the interaction between various modules.

👉 Helps you with an easier risk mitigation

Synthetic tests, by catching issues within isolated components, contribute to risk mitigation by preventing such problems from escalating. While end-to-end tests are crucial for identifying integration issues.

👉 You get higher confidence in the system's quality

Integrating both types of tests into CI/CD pipelines ensures that code changes are thoroughly tested before deployment. Synthetic tests can quickly catch issues in individual components, while end-to-end tests provide confidence in the overall application functionality.

Synthetic tests and end-to-end (e2e) tests play distinct yet complementary roles in a comprehensive software testing strategy. Automation facilitates their integration into continuous testing pipelines, ensuring efficient testing throughout the development lifecycle.