basic-tdd-flow-rspec.md

Basic TDD Flow with rspec

To create a new project with rspec, begin from the the project's root directory and install the rspec gem:

gem install rspec

Create a folder in this root directory called spec where we will house all of your test files. cd into this folder and create a file called reverser_spec.rb. Let's write our first test:

describe 'Testing' do
  it "should be true" do
    expect(true).to be true
  end
end

Run the test with the following command:

rspec spec/reverser_spec.rb

This test will pass because you are asserting that true is true (which it is). Let's change the test to call our Reverser class:

describe 'Reverser' do
  it "should reverse a word" do
    reverser = Reverser.new
    expect(true).to be true
  end
end

You should get an error uninitialized constant Reverser. That's because we haven't created the Reverser class yet. Go back to the root and create a file called reverser.rb and create the class:

class Reverser
end

Since you are now trying to refer to a different file, we have to amend the first line of the test file to require_relative '../reverser'. Try running your test again; it should pass.

Now let's write a more meaningful test:

require_relative '../reverser'

describe 'Reverser' do
  it "should reverse a word" do
    reverser = Reverser.new
    expect(reverser.reverse_word("hello")).to eq "olleh"
  end
end

Now run your tests. This error should make sense. You don't have a reverse_word method in your Reverser class. Let's add that.

class Reverser
  def reverse_word(word)
    word.reverse
  end
end

Run your tests. You now have a test-driven-developed method!