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RSpec is a behavior-driven testing tool for the Ruby language.  RSpec is used in test driven development (“TDD”), where the developer writes the test based on what s/he hopes the program will accomplish, and then creates the program to accomplish the goals of the test.

While this would seem to create additional work for the developer, it actually saves time in the development process as the developer is more easily able to tell whether the program is functioning properly.

Installing RSpec

We’ll start by making sure you have  rspec installed.  If you don’t, you can easily install  rspec  with gem install rspec.

Setting Up Our Directory and Test Suite

To begin, we’ll create a directory called  school  using mkdir school.  We’ll then migrate to our school directory and create a file called student.rb using touch student.rb at the command line.

It’s now time for us to create our test suite.  To do this, we’ll create a directory inside the school directory called  spec by running mkdir spec.  Inside the  spec directory, we’ll create two files: student_spec.rb and spec_helper.rb using touch student_spec.rb and touch spec_helper.rb.

There should be one spec file per class.  However, even with multiple classes, we only need one spec_helper, as the spec_helper exists to  require the Ruby classes we’re testing.

spec_helper.rb

Inside our spec_helper file, we need to require our Ruby classes:

require_relative '../student'

require_relative is used to require a directory or file relative to the current directory.

student_spec.rb

In student_spec, we’ll create the tests needed to ensure our Ruby code in student.rb is running properly.  The first thing we’ll want to do is  require the spec_helper with  require_relative 'spec_helper.rb'.  We’ll then want to create a shell for our specs.  Our file thus far will look something like:

describe simply describes what we’re testing which, in this case, is the class Student.

Ideally, we’d like a program that will keep track of all students at our school. To do this, we want our program to be able to initialize a student, save the student’s name so it cannot be changed, and be able to list all of the students.  To do this, our code will look something like:

Let’s break down the above code:  We are describing the student class, and the things we’d like the class to do.  Each time we run  rspec, we want our class to reset itself with a method called reset_all.  This is because each time we run  rspec we will create a new instance of the class, and our tests will be compromised.

After the reset, we want our class to accomplish 4 things: (1) it can initialize a student, (2) it can initialize a student with a name, (3) it should not allow a student’s name to be changed, and (4) it should keep track of how many students have been initialized.  Of course, due to the reset, this will always be 1 when we run  rspec, though this just ensures the program is functioning properly.  In reality, there will likely be many more instances of the student class.

Running RSpec

When we first run  rspec, we are unable to see our examples and errors.  Instead we get the following error:

As you can see, this error says we have an uninitialized constant Student:  /Users/korenlcohen/Flatiron/school/spec/students_spec.rb:3:in `<top (required)>': uninitialized constant Student (NameError) .  To correct this error, we simply need to create a student class in student.rb:

Once our class has been created, rspec will run properly:

As you can see, we have 4 examples and 4 failures.  Assuming you know simple Ruby, you’ll be able to make these tests pass quickly with the following code:

If you run the test now, we’ll have 0 errors.  Of course, as your programs become more complicated and must accomplish a greater number of tasks, your test suite will become comparably more complicated.

RSpec Tips

When you’re working with a test suite that contains multiple examples, sometimes it helps to streamline the process by using rspec --fail-fast.  This will generate a single failure at a time, so you can easily zero in on an error instead of scrolling through multiple failures at the same time.

If you want your examples and failures to appear in color, you can use rspec -c.

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Koren Leslie Cohen

Product manager at Facebook. Former senior product manager at Dollar Shave Club in Los Angeles and software engineer at J.Crew / Madewell in New York City. Recovering trial lawyer.

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Latest posts by Koren Leslie Cohen (see all)

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