What kinds of Rails tests I write and what kinds I don’t

by Jason Swett,

The challenge of deciding what kinds of tests to write

There are a lot of different kinds of tests a developer could possibly write. In RSpec there are model specs, feature specs, view specs, helper specs, routing specs, controller specs, and request specs. Do you need to write all these different types of tests? If not, which ones should you skip?

The two types of tests I write

In my Rails apps I usually only write two kinds of tests. To use framework-agnostic language, I write model tests and acceptance tests. To use RSpec-specific language, I write model specs and feature specs. Let’s talk about each of these two in a little more detail.

Model tests are relatively isolated. A model test will test the behavior of a particular Ruby class in my Rails application, e.g. the Customer model. Model tests are what give me confidence that my features are working at a fine grain. (I often use the terms “class” and “model” somewhat interchangeably since a Rails model takes the form of a Ruby class.) For example, if I have a method that returns the grand total of the payments a certain customer has made, I’ll write a model test for that method.

What about acceptance tests? Whereas model tests are relatively isolated, acceptance tests are the opposite; they’re relatively integrated. An acceptance test exercises the whole stack, browser and all. Acceptance tests give me confidence that everything works together. For example, if I have CRUD functionality for a Customer resource, I’ll write acceptance tests for creating a customer, updating a customer, and deleting a customer.

A note on terminology

As of the time of this writing there not complete consensus in the testing world on testing terminology (and I don’t expect this to change anytime soon). For example, some developers might consider the terms end-to-end-test, integration test, and acceptance test to refer to basically the same thing, whereas other developers might consider these three terms to refer to three completely distinct types of tests.

What does this mean for you in terms of your testing journey? It means that if you, for example, see a reference to end-to-end tests that doesn’t square with your understanding of the term end-to-end tests, that doesn’t necessarily mean that your understanding is mistaken, it just means that not everyone in the testing world talks about the same concepts using the same exact terms. I think understanding this communication challenge is helpful since otherwise one might get distracted by all the apparent discrepancies.

Testing terminology + RSpec

How do model tests and acceptance tests map to RSpec? Model tests—or model “specs” in RSpec terminology—are the tests that live in the spec/models directory. Nothing but bare RSpec is needed in order to write model specs. What the outside world calls acceptance tests (or again, integration tests or end-to-end tests) are known in RSpec as feature specs. Since feature specs exercise features via the browser, the Capybara library (a library that allows us to manipulate the browser using Ruby) is necessary.

Why, by the way, is an RSpec test called a “spec” instead of a “test”? The idea is that each RSpec file is an “executable specification”. Each test case is actually called an example in RSpec terminology, an example of how that feature is supposed to behave. A set of examples makes up a spec. Personally, I’m willing to play along with this terminology to some extent, but I frankly find it kind of annoying. You’ll find that most of the time I say “test” instead of “spec” or “example”.

The types of tests I don’t write

I typically don’t write view specs, routing specs, or request specs/controller specs. Let’s discuss each of these.

Request specs/controller specs

First, a bit of terminology: request specs and controller specs are two very slightly different things, although for our purposes we can treat the two terms as meaning the same thing. A close enough approximation to the truth is that “controller spec” is the old name and “request spec” is the new name.

I usually don’t write controller/request specs (although I do sometimes). The reason is that I try to have as little code in my controllers as possible. For the most part, my controllers don’t do anything, they just call model objects that do things. Any code that might have been covered by a controller/request spec, I prefer to cover via a feature spec.

View specs, routing specs

I don’t write view specs and I don’t believe I’ve ever encountered anyone who does. The reason is that I’ve never been able to conceive of how a view spec could have value that a feature spec doesn’t already provide.

I also don’t write routing specs, and for the same reason. I find them to be redundant to feature specs.

Conclusion

If you’re just getting started with Rails/RSpec testing and you’re wondering which types of tests to focus on, I would recommend focusing on model specs and feature specs.

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3 thoughts on “What kinds of Rails tests I write and what kinds I don’t

  1. Ross Hunter

    When I am testing an API, I call my tests that hit the endpoints from the “outside” request specs — though for the purposes of the API they are end-to-end…

    Terminology is hard.

    Reply

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