Introduction to Testing Distributed Systems

Among the types of tests that are needed to write and maintain proper software, unit tests are not affected by scalability. Whatever your code base size, the way to write and execute those tests stays the same. Such checks are not tied to anything other than simple units of code, and they should not be dependent on the global application architecture.

However, most of the time, this cannot be said of functional tests. They can depend on other services if the application has been built using a micro-services architecture, for example. The same goes if an application depends on an external system, storage, relational database, etc.

Writing microservices is an excellent solution for distributing your application among several nodes. The problem is that testing the multiple parts together might be tricky.