Testing Microservices? Here’s a Guide on Designing a Strategy!

Almost all businesses use microservices.

At a basic level, microservices make up applications. They’re small and compact files that provide a multitude of services.

They’re programmed to ensure decentralized management (especially for data storage). And they’re designed for quick access too.

We use them in our daily lives, and for a variety of functions. They can be anything from productivity applications, to small games, or special professional programs.

Testing a Microservice

A bundle of microservices make up an application. And it’s important to test each microservice separately and in conjunction with each other.

That’s one of the pros of a microservice. They launch separate of others within an application. And this lets you deploy and test each without problems.

From there on, we’ll need to plan our approach for testing. Specifically, we’ll need to…

  • Understand different testing types.
  • Understand different testing strategies.

We’ll explore both below. We’ll mention the 5 testing types and the best strategies for each.

1. Unit Testing

While contract testing checks for communication, unit testing checks for coding. It ensures that a microservice does what it’s supposed to do with each test.

And here, a unit represents the smallest possible portion of a microservice that can be tested.

With unit testing, it’s key to test each unit in isolation. After that, units can be tested together (integration testing). And this ensures that microservices collaborate well in an application.

Important Note

This tends to be the first type of microservice testing that’s performed. It’s usually performed during the development process (instead of before deployment).

This makes it a cost-effective form of testing. It aids developers in finding errors early in design, without the need for prolonged testing afterwards.

Plus, the changes can be done quickly – which saves more money.

Testing Strategy

Unit testing is straightforward. It involves taking a microservice, creating a mock object (as a replacement for codes yet to be designed). From there, the unit is tested for proper coding.

There is a multitude of unit testing tools (and for different programming languages). They include,

  • Junit (a free tool for Java).
  • JMockit (an open-source tool with verification syntax and API).
  • NUnit (a framework that works with .net languages).

2. Functionality Testing

This is the beta stage of most apps and software. Here, microservices are tested from a user perspective.

This form of testing can be jammed anywhere in the design stage. Functions can be tested with each microservice. Or, they can be done at the end, testing the functionality of the entire system.

Important Note

What makes functionality testing different from unit testing is the focus. Unit testing focuses on how codes are executed.

It tries to find errors beforehand per microservice.

With functionality testing, the program is handled from an “end-user” perspective. It’s used as if the consumer was using it. The results are then noted down before any adjustments are made.

Testing Strategy

Functionality testing should be done after unit testing for smaller apps. For larger ones, we recommend delaying the process to the end.

It can, however, be executed for larger apps through the design process – by testing the functions of unrelated components separately.

3. Integration Testing

What happens after a unit is tested? What happens after functionality is checked?

Several units are banded up together and tested. This is called integration testing, and it checks as to how each unit communicates with each other.

The focus here differs from unit testing. While unit testing checks for functionality, integration testing looks for defects when multiple microservices interact.

Strategy for Integration Testing

One is called the “Big Bang”strategy. It involves testing all microservices together after development is complete.

This strategy saves time, ensuring that integration testing isn’t done frequently. But it comes with the drawback of pinpointing errors.

When an error message (or an undesired result) is presented, it’s hard to tell which microservice is at fault. It’s also difficult to tell which coding line is responsible.

Thus, this strategy works for small applications only (ones with a minor amount of microservices – and little upgrades).

As for larger applications, we recommend an “incremental strategy.” Here, microservices are categorized (as to how they logically relate to each other).

Then, they’re tested for proper functionality. While this strategy isn’t as comprehensive as the previous – it works well for large applications that require frequent updates.

4. Contract Testing

A microservice communicates between a client and an API provider. And with a contract test, a developer can tell if any communication issues exist.

Contract testing focuses on setting an endpoint through testing. Tests are done until the desired response is found after multiple tries.

Coding lines are changed in accordance with the results of each trial.

Contract testing looks at the program from an end-user perspective (like functionality testing).

It ensures that a user operates each microservice smoothly and without issues. And if any disruptions happen through the experience, then they’re fixed.

Why They’re Necessary

They’re vital for documenting the final product. Contract testing is what defines the advertised “specs” of a program.

It sets the system requirements, speed, and effectiveness of the app.

As a result, this form of testing is always done after an app is completed. It’s done to ensure that the final product hits the specification goals set by a business.

The Right Strategy

Contract testing should only be done to optimize microservices “per business specifications.” Not every microservice should be tweaked for maximum performance. This should be left to the business to define.

5. End to End Testing

This is similar to integration testing. In fact, it’s a combination of contract and integration testing, only on a large scale.

Here, the focus is on the system as a whole. This, it includes backend systems and interfaces too. And what’s being tested is the entire system before deployment.

The goal is to ensure that the entire system works as specified (irrespective of individual microservices).

How This Affects Microservices

Microservices can be tweaked as a result of end-to-end testing. This form of testing ensures that the right code branches are used in a program.

And if there are any missing functions, then the tests check for microservices that can fill in the blanks.


This tends to be the longest form of testing in any application’s design.

A good strategy is to create test cases. They should be executed, with the results being compared against the desired outcomes.

This form of testing should be done manually. It’s difficult to automate since the entire system’s components work at the same time.

Its amount of times should be limited. Being an exhaustive form of testing, it can cost a business too much when designing an application.

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Creating a Comprehensive Testing Strategy

One of the problems with the microservice design is how you plan to test. You can mix and match the forms of testing you do.

You can also schedule different tests for different times (throughout the design cycle).

Basically, what works for one app may not work for another. Thus, we recommend consulting previous projects when designing a test strategy.

That way, you can fully test your codes with minimal time and financial investment!

Author: Pradeep Parthiban
Pradeep is a Content Writer and Digital Marketing Specialist at Indium Software with a demonstrated history of working in the information technology and services industry.