7 best Ruby Functional testing libraries in 2025

Functional testing is the process of checking that individual software components are working as expected. It is intended to verify the correctness of a system’s behavior by inputting data and checking the output values. With the rise in popularity of Ruby, many developers are working on new applications and APIs. As a result, this has led to the emergence of a number of testing libraries that have come along to make their lives much easier. Here we will discuss some of the best Ruby Functional testing Open Source libraries including factory_bot - A library for setting up Ruby objects as test data; shoulda-matchers - Simple oneliner tests for common Rails functionality; appraisal - Ruby library for testing your library against different versions.