Contract Testing

Published on: Jan 02, 2023

Contract Testing and Its Advantages in the Microservices World 

When working on a vast system and developing microservices, web apps, and mobile applications, we disrupt the system every time, and one of these components is updated. Testing, particularly regression and integration testing, is complicated and time-consuming.  

End-to-end integration tests are often ineffective when the systems are very dispersed and complicated since they overlook numerous cases due to message variants. Preparing test data also becomes a substantial task. As a consequence of this necessity, a new testing category was created.  

Contract Testing is used to verify interfaces in big, highly dispersed systems. The testing assures that two different methods (for example, two microservices) are compatible and can interact. It records the interactions between each service and stores them in a contract that may subsequently be used to verify that both parties follow it. 

Contract testing offers an intriguing value proposition. Generally, when dealing with extensive distributed systems, this testing is less expensive and more convenient than end-to-end testing. As a result, they are less costly and quicker than end-to-end testing, which requires a whole environment. 

To reduce the requirement for end-to-end testing, tools such as “pact” from have gained popularity. Writing a pact contract test for the scenarios of a contract between a publisher and a consumer service, for example, is as easy as declaring the schema they agree to use. According to our experience, there is also a reasonably short learning curve, and one-time setup work to consider. 

Pact is challenging to set up, but it is the best open-source version. It is necessary to configure the interaction server and scripts to run the publisher and consumer test cases. The contract tests will take no more than 5 to 10 minutes to write, which is strikingly comparable to constructing a Unit-test case. The setup and first contract testing will take at most 3 hours.