Ruby module can be used to group methods and constants together. This tutorial illustrates testing of ruby module either in isolation or based on the class where it is included or extended.

Testing module / self methods

Let’s take a simple example of a Ruby module which contains self (module) methods.

module MyModule
  def self.hello
    puts "Hello"
  end
end

Now, testing of such a module can be done in isolation by calling the class method directly from module.

Below is the rspec test code for the above module.

require 'spec_helper'

RSpec.describe MyModule do
  it "should say hello" do
    expect(MyModule.hello).to eq("Hello")
  end
end

Testing instance methods

Now, let’s take a look at the same example with a class which includes the module to test instance methods on a module.

module MyCalendar
  def number_of_months
    12
  end
end

Now, to test this module, we shall include this module in a dummy class. Then, we test the behaviour of the module method by calling the method on an object of the dummy class.

require 'spec_helper'

class DummyCalendar
  include MyCalendar
end

RSpec.describe MyModule do
  it "should say number of months" do
    calendar = DummyCalendar.new
    expect(calendar.number_of_months).to eq(12)
  end
end

This will test the module method based on a dummy class. In this way, we don’t need to test the behavior of all the classes where this module is included.