Level Up 3: Writes meaningful tests, and knows what tautological tests are

gistfile1.txt

Suppose we have a Rails model: Article

In the following tautological test, we aren't testing the the #camel_case_title method is actually doing anything:

describe Article, '#camel_case_title' do

  it 'returns the title in camel case format' do
    article = double(:article)
    article.stub(:camel_case_title).and_return("The_Best_Article")
    
    expect(article.camel_case_title).to eq("TheBestArticle")
  end
end

But if you look at the implementation of this method in the model, it looks like this:

class Article < ActiveRecord::Base
  def camel_case_title
    title.camelize # This uses ActiveSupport's camelize method
  end
end

If you notice, the real method should return "TheBestArticle", but our stubbed version returns "The_Best_Article". Thus, the test isn't actually testing the implementation of this model method. In fact, it is simply testing that stubbing works.

In the correct implementation of the test, we would create an article with a title attribute. Then we would exercise the #camel_case_title method on this instance, and confirm the camelized title is returned:

describe Article, '#camel_case_title' do

  it 'returns the title in camel case format' do
    article = Article.create(title: "The best article")

    expect(article.camel_case_title).to eq("TheBestArticle")
  end
end