A unit test is about testing a single function/method in isolation with all of its possible outputs.
A functional test is about testing a single functionality, which can span multiple methods and a controller.
Other common terms in Rails are "model tests," "controller tests," and others.
You can find model tests in
spec/models, controller tests in
spec/controllers and additional functional tests in various directories within the
You can run all models tests, for example, with:
bundle exec rspec spec/models
To run an individual file you can use, for example:
bundle exec rspec spec/models/user_spec.rb
To run a specific test case you can use, for example:
bundle exec rspec spec/models/user_spec.rb:10
10 is the line number of the test case that you want to execute.
Historically, it has been common to use Rspec to write tests for Rails controllers. This pattern isn't necessarily discouraged in the DEV codebase, but Rspec has introduced a more effective way to test controllers via Request Specs.
Request specs test the actions on a controller across the entire stack, effectively acting as Integration Tests. You can read more about request specs in our documentation on Integration Tests.
You can read the official guide Testing Rails Applications to learn more.