Microservices Testing: 6 Must-Have Test Types

What is Microservices Testing?

Microservices are a style of software development architecture that divides applications into loosely coupled sets of services. Each service is self-sufficient and does one thing well. One of the benefits of this architecture is that it allows fast, continuous deployments. It is also possible to easily roll back a specific service and check for problems, whereas in a traditional monolithic architecture it is necessary to test the entire system.

Microservices are becoming a mainstream software architecture, and just like monolithic applications, they need to be tested to ensure quality. Microservices testing has two aspects – testing each individual microservice to see if it performs its desired function, and testing the entire microservices application to see if microservices work well together and correctly serve user requests.

Testing microservices can be difficult, due to the complexity of microservices architectures. It can be hard to make microservices observable, and teams need to manage the continued evolution of new microservices – different teams develop different microservices, often with limited communication between them. This can make it difficult to decide what and how to test.

Microservices Testing Challenges

Testing microservices-based systems pose unique challenges that cannot be addressed by traditional testing techniques. If you try to test all service components simultaneously in the same environment using traditional testing, you will not get a realistic result. A microservices application works differently in production, meaning service components are usually unavailable in the same form or the same environment. 

Testing changes

A service component implementing an API (a service provider) remains unaware of the other components using its API (service consumers). As a result, once a provider microservice gets updated, you cannot guarantee it will not disrupt the API’s functionality, even if you have thoroughly tested the changes. You can set up a test environment that tests this process from end to end, but this is typically costly and complex. 

Manual testing

You can perform extensive manual testing during build phases to detect service interaction issues. However, microservices applications often have many components, making it difficult to observe accurate behavior in development. You might find it easier to fully understand the behavior of components when observing the application in production. 

Must-Have Test Types in Your Microservices Environment

To ensure microservices applications are high quality and secure, you must implement at least the following test types in your environment.

1. Unit Testing

Unit testing helps you verify each component’s code aligns with business logic. Each software component unit has a different size, ranging from a few lines of code to large blocks. Large units of services typically yield complex tests because they scale resource utilization over time. To test your microservices accurately, you must keep all test units small. 

2. Integration Testing

Integration tests help validate a unit’s functionality as it works with other units and dependencies. Multiple microservices typically interact and execute together to achieve a specific business goal. To ensure communication channels function as intended, you must monitor all requests flowing through these services.

3. Component Testing

To verify that a microservice works as expected, you must test the complete use cases or processes within each component. You can speed up execution by substituting external dependencies with in-process mocks. A component test should start with a certain business feature request through an exposed interface. You verify expected results using public interfaces or checking mock pattern usage.

4. Contract Testing

Contract testing verifies that services communicating with external third-party software components meet legal requirements. Tested calls and responses can pass a contract test by producing the same results each time, even when the service is upgraded or altered.

Contract testing is critical when many distributed services run application components in production. When conducting contract testing on microservices, you must ensure that the service producer and consumer include an up-to-date contract version.

5. Penetration Testing

A penetration test (pentest) launches an authorized cyberattack simulation on a computer system or network to evaluate its resiliency to malicious attacks. It works similarly when testing microservices and web applications. The goal is to test several flaws in the application or system. 

Microservices and APIs can introduce many API security and web vulnerabilities into an application, including those mentioned in the OWASP Top 10 list. You can use pentesting to see how your microservices fare against these common attacks. However, ideally, you should look for attacks that affect microservices and APIs the most, including: 

• API-particular Distributed Denial of Service (DDoS) attacks
• Custom authentication and authorization weaknesses
• Binary deserialization/parsing attacks
• Rate limiting/throttling bypasses

6. End to End Testing

End to end (E2E) tests help validate the entire journey. It involves running the entire microservice system with the same setup as a production environment to check whether the user’s journey is completed. End to end tests are highly versatile but also complex and fragile.

Tips for Testing Microservices

Here are best practices to help you develop a microservices testing strategy:

• Think of each service as a software module—as with any new code, a microservice should have unit tests. In a microservices application, all services are treated as black boxes, so each one needs to be individually tested.
• Identify and test critical connections—for example, test the integrations that represent a single point of failure for the application, such as connections between the login service and functional service, and the connection between the frontend service and the database.
• Consider both positive and negative scenarios—microservices can fail, and simulating failure scenarios is critical to building system resiliency.
• Shift testing left—start testing in the early development phase and continue to test throughout the development lifecycle. Use a combination of different testing techniques to find as many issues as early as possible. This is not only more likely to find bugs, but also makes bug fixes easier and more efficient. This can lead to complex virtual environments with nuances between the various libraries, and despite the visualization layer, the underlying hardware architecture can lead to unexpected results. this is
• Use canary testing—test your new code on a small sample of real users. Controlled testing in production is the best way to validate a new release. Use microservices monitoring tools, and select the most relevant metrics to indicate if a test has passed or failed.

Conclusion

In this article, I explained the basics of Microservices testing and the test types in a microservices environment:

• Unit testing—unit testing helps you verify each component’s code aligns with business logic.
• Integration testing—integration tests help validate a unit’s functionality as it works with other units and dependencies.
• Component testing—To verify that a microservice works as expected, you must test the complete use cases or processes within each component.
• Contract testing—Contract testing verifies that services communicating with external third-party software components meet legal requirements.
• Penetration testing—a penetration test launches an authorized cyberattack simulation on a computer system or network to evaluate its resiliency to malicious attacks.
• End to end testing—End to end tests involve running the entire microservice system with the same setup as a production environment to check whether the user’s journey is completed.

I hope this will be useful as you level up microservices testing in your organization.