Microservices Testing: A Comprehensive Insight and Approach

Applying the single responsibility concept at the architectural level leads to a microservice architecture. Compared to a traditional monolithic design, it has a lot of benefits, including autonomous deployability, language, platform, and technology independence for individual components, discrete axes of scaling, and increased architectural flexibility. REST is preferable over HTTP for microservice integration.

Microservices architecture impacts the development and testing of software applications and often exhibits a similar internal structure made up of part or all the visible layers. Any testing approach should strive to cover every layer and every gap between different service levels while being compact. When you adopt a microservices design, previously concealed boundaries become visible because of the granularity. Because of this, test managers must approach the testing of microservices very differently.


Microservices testing has been the most frequent issue seen in software testing. Teams have reported running into problems while switching to a microservices architecture. This issue arises because they are unsure of the microservice testing approaches they want to employ. It is usually apt for a team that has just started with microservices. Your testing strategy and environments should account for a microservices architecture that relies more on remote dependencies and less on in-process components.

The more coarse-grained a test is regarding microservices testing, the more fragile and time-consuming it is to write, perform, and maintain. The idea aids in our comprehension of the proportion of tests required at each level of granularity. Mike Cohn's test pyramid explains this in great detail.

Microservice Testing Pyramid

The range of the tests broadens as we approach the upper tiers of the pyramid, while the quantity of tests diminishes.

Unit Testing

The foundation of microservices is decomposing business logic into its smaller components. Then, these services interact with one another via a network. Therefore, it is even more crucial to use unit testing to verify each piece of business logic. A unit test runs the smallest testable part of code in the application to see if it performs as expected. The size of the testing units is undefined, but ideally, it should be as small as possible. It is easier to define the behavior when the test is narrow since the unit's branching complexity is lower. There are two approaches to unit testing:

When a module is divided into discrete, more logical sections and tested separately, it becomes challenging to create a unit test. The unit test may not always yield significant benefits. The complexity of the test suit and the size of the microservices are inversely correlated. The complexity of a service grows as its size decreases. The test outfit should always be lightweight, narrowly focused, and valuable. Tests run faster when their scope is restricted. Unit tests are critical for microservices because they provide focus and behavior. Its testing's goal is to limit the behavior of the unit under testing. But Regrettably, testing also places limitations on implementation procedures. As a result, it raises the question of how valuable a unit test is and how much money it costs to maintain.

Integration Testing

Microservices are brought together for an integration test to ensure they work together as planned to complete a larger piece of business logic. It also tests the communication flow through a subsystem to look for erroneous presumptions. Integration tests can be of any granularity; however, for microservices, usage determines granularity. It's crucial to keep your final aim in mind when creating an integration suit. The integration module's only objectives should be success and error paths. Every request in the integration test would contact several services before returning to the user with a response, which is what takes place. Therefore, observability and monitoring of requests across services become crucial.

Uber, one of the largest businesses to use microservices, has long struggled with testing. Integration testing is like a black hole for endless engineering cycles with no equivalent payback. Testing in microservices was a nightmare due to the enormous obstacles, but then the Step-Up Rule was introduced. This model recommends testing at a layer higher than what is often advisable. Unit tests would resemble integration tests; integration tests would look like testing on actual production, and testing done on the production environment would be like monitoring and exploration.

Component Testing 

After unit testing each function in a microservice, it's time to test the microservice independently. A component test isolates the code under test from other components and restricts the scope of the exercised software to a specific area of the system under test. It does this by influencing the systemt hrough internal code interfaces. Each microservice's source repository should incorporate component testing. There will be several microservices in a typical application. The other microservices must be recreated or mocked to test a single microservice in isolation. Using test doubles to isolate microservices prevents any complex behavior they might exert on execution.

The API behavior is driven by writing tests at the microservices layer's granularity. The component tests will simultaneously examine how microservices interact with the database. Component testing's key advantage is that it enables isolation testing of microservices, which is better, quicker, more reliable, and less expensive. Microservices may pass the tests, but the application may still malfunction in production, which is a significant downside and raises an important issue.

How to guarantee that invoked services behavior is replicable by the tests?

Contract Testing

A contract between two parties happens when a consumer connects to a component's interface to use its functionality. What do the consumer and the component exchange? Its side effects are performance, concurrency, and input and output data structures. Microservices serve as a unit of encapsulation, which is one of the fundamental aspects of its architecture. Each service has a contract with the other via an API. Contract testing reveals distinct programming languages, stacks, and design patterns across each service. As a tester, you must create an impartial test plan that only validates the operational aspects of service production.

Before starting, do remember a few things:

End-to-End Testing

A system is thoroughly tested from beginning to end in an end-to-end test to ensure that it satisfies external requirements and accomplishes its objectives, for which the system operates as a black box. The tests manipulate the system through open interfaces while exercising as much of the fully deployed system as possible. Before writing an end-to-end test suit, these are the guidelines to remember:

A microservice architecture can evolve due to end-to-end tests. End-to-end test censure that the business functions provided by the system throughout such significant architectural refactoring do not suffer because of the service's probability of splitting or merging while learning about the problem domain.

Testing Tools

When dealing with microservices, you can employ the testing tools indicated below.

Final Words

Contract Testing is one that you must include in your thorough release procedure. Performance contract testing combines manual testing with additional tests like automated unit testing, load testing, and integration testing. It will give you general process quality assurance.

Microservice testing is now more critical than ever because most BIG corporations, like Netflix, Amazon, and Uber, have shifted to using them. We are more than happy to help you if you need any advice, have any queries, or are having trouble setting up a productive microservices testing pipeline.

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