Here’s an incomplete list of tools and concepts you might encounter when first trying to learn Rails testing: Capybara, Cucumber, Database Cleaner, factory_bot, Faker, MiniTest, RSpec, system tests, Test::Unit, acceptance tests, end-to-end-tests, mocks, stubs, unit tests and TDD.
The challenge of getting started with testing would be much easier if you knew exactly what you needed to know and what you could safely ignore. What follows is a list of what you can safely ignore.
You don’t need to get hung up on which framework to use. You literally can’t go wrong. The principles of testing are the same no matter which testing framework you use. Plus you can always change your mind later.
When I first got started with Rails, the way I decided on a testing framework was very simple. I noticed that most Rails developers used RSpec, so I just picked RSpec.
Most Rails test suites have two main sub-suites: a suite of model tests and a suite of integration tests.
Model tests test the behavior of ActiveRecord models by themselves. Integration tests actually spin up a browser and do things like fill out forms and click links and buttons as if a human is actually using the application.
Between these two, the bar is lower for model tests. For integration tests you have to do almost all the same stuff as model tests plus more. For this reason I suggest that if you’re a newcomer to Rails testing that you start with model tests (or even just Ruby tests without Rails) and ignore integration tests altogether until you get more comfortable with testing.
So you can ignore Cucumber (which I don’t recommend using at all), Capybara and system tests, which are all integration testing tools.
I’ve never written a view spec. To me they seem tautological. I’ve also never encountered any other Rails developer who advocates writing view specs.
If for some reason I had a wildly complicated view, I could see a view spec potentially making sense. But I haven’t yet encountered that case.
I don’t tend to write helper specs because I don’t tend to write helpers. Helpers are a fairly peripheral area of Rails that you can safely disregard altogether when you’re getting started with Rails testing.
Like view specs, I find routing specs to be tautological. I don’t write them.
Request specs are a great boon and even necessity if your application has an API or if your controllers do anything non-trivial. But I don’t think you should worry about request specs when you’re just getting started.
Controller specs are deprecated in favor of request specs.
The main thing I would recommend learning when you’re getting started with Rails testing is model tests.
When you’re learning about model tests you’ll naturally have to get acquainted with RSpec syntax (or whichever framework you choose), factory_bot and Database Cleaner (or analogous tools). But other than the actual testing techniques, that’s about it as far as model test tooling goes.
If you want to make life even easier on yourself you can learn just Ruby and RSpec with no Rails involved. Then, after you get comfortable with RSpec syntax and basic testing techniques, you can approach Rails testing with more confidence.