How is testing different in monolith and microservices architectures?
Tags: architecture, microservices, devops, devtips
Published: 2022-05-03 14:41:35

Testing is an integral part of any application in order to deploy quality products to meet the customer’s business requirements. However, testing can pose different challenges based on the application’s architecture. Over the years, I have seen organizations sometimes struggle with writing test cases and test scenarios based on the application’s architecture. Between [monoliths vs. microservices](https://www.simform.com/blog/monoliths-vs-microservices/), testing is easier in the case of monoliths architecture. There is only one codebase to go through and track while testing and debugging. While if we talk of the microservices architecture, comprehensive testing is always a challenge. 

You are supposed to test out each microservice individually, but you also need to pay great attention to the testing of inter-microservice interaction. Business flows usually go through multiple microservices, and QA teams need to cover all the possible interaction scenarios. 

In terms of failure, microservices also come with the cushion of failure isolation. If some things go down, it’s less likely that the entire application will go down. However, in the case of monolithic applications, there are multiple potential single points of failure.


##How is testing different in Monolithic architecture?

A monolithic application is composed of a single chunk of the codebase that holds multiple application features. The [drawback of this architecture](https://blog.clairvoyantsoft.com/monolith-and-microservices-testing-564061859843) is that sometimes it can expose a few of its APIs to be consumed by third-party vendors. Monolithic architecture is perfect where frequent updates are not a necessity. Otherwise, adapting to the requirement changes and scaling will increase the cost of development and testing by multiple folds. 


##How is testing different in Microservices architecture?

Microservices architecture comprises a set of individual applications that can be independently built, deployed, tested, and released. Unlike testing in chunks, microservices give us the liberty to develop and test applications in units that helps in the quick release of the application. Just like monoliths architecture, microservices also expose APIs, but as monoliths consist of all the features together, exposure of API can affect the whole application. On the contrary, microservices might expose public as well as few private APIs for the purpose of testing. Initially, it might seem like additional work, but in the long term, it saves cost. 

##Testing: Microservices vs. Monoliths 

Both the architecture reacts quite differently while testing is conducted.  

Unit testing is written by the developer to check the correct logic and functionality of the developed feature. It is crucial for both monolithic and microservices architecture. However, there is no difference in the way how unit testing needs to be performed based on architectural changes.   

Integration testing is performed to find bugs not covered by the unit testing. The application is thoroughly tested for bugs like misuse of API and threading concurrency in this testing type. Integration testing is very crucial for the monolithic architecture as it deals with API exposure problems. However, the point to be noted here is that preparing the application for integration testing is usually not a challenging task. Whereas microservices architecture usually requires distinct build systems for individual microservices that need to be deployed and tested. As a result, the integration framework for microservices architecture becomes much more complex in nature.  

As microservices share a couple of both public and private APIs, contract testing is especially beneficial for the architecture. Here is how it works: All the consumers of a particular API share their contract with the API provider, and the provider verifies the compliance of the contract. Otherwise, there will be multiple sets of requests/responses between the provider and the consumer. For identifying the misuse of APIs, contract testing is far more efficient than integration testing. 


##Conclusion

As you must have noticed, both the architecture have its boons and banes. While monolithic architecture is better suited for simple, lightweight applications, microservices are suited to keeping scalability in mind. In terms of testing, both have their challenges, as discussed above. Do you know any specific challenges you encountered while working on them? Kindly share them in the comments below.