Homework 3: Behavior-Driven Design

In this homework you will create user stories to describe a feature of a SaaS app, use the Cucumber tool to turn those stories into executable acceptance tests, and run the tests against your SaaS app.

Specifically, you will write Cucumber scenarios that test the happy paths of parts 1-3 of HW 2. The GitHub repo

saasbook/hw3_rottenpotatoes

contains a "canonical" solution to HW 2 against which to write your scenarios. It also contains the necessary scaffolding for the first couple of scenarios. We suggest you first fork that repo on GitHub, then clone from your own fork:

git clone [email protected]:YourGitHubAccount/hw3_rottenpotatoes.git

We recommend that you do a

git commit

as you get each part working. As an optional additional help, git allows you to associate tags -- symbolic names -- with particular commits. For example, immediately after doing a commit, you could say

git tag hw3-part1b

and thereafter you could use

git diff hw3-part1b

to see differences since that commit, rather than remembering its commit ID. Note that after creating a tag in your local repo, you need to say

git push origin --tags

to push the tags to a remote. (Tags are ignored by deployment remotes such as Heroku, so there's no point in pushing tags there.)

Create a declarative scenario step for adding movies

As explained in Section 4.7 of Engineering Long-Lasting Software, the goal of BDD is to express behavioral tasks rather than low-level operations.

The background step of all the scenarios in this homework requires that the movies database contain some movies. Analogous to the explanation in Section 4.7, it would go against the goal of BDD to do this by writing scenarios that spell out every interaction required to add a new movie, since adding new movies is not what these scenarios are about.

Recall that the Given steps of a user story specify the initial state of the system; it doesn't matter how the system got into that state. For part 1, therefore, you will create a step definition that will match the step, "Given the following movies exist" in the Background section of both sort_movie_list.feature and filter_movie_list.feature. (Later in the course, we will show how to DRY out the repeated Background sections in the two feature files.)

Add your code in the movie_steps.rb step definition file. You can just use ActiveRecord calls to directly add movies to the database; it's OK to bypass the GUI associated with creating new movies, since that's not what these scenarios are testing.

Success is when all Background steps for the scenarios in filter_movie_list.feature and sort_movie_list.feature are passing green.

Happy paths for filtering movies

Complete the scenario restrict to movies with 'PG' or 'R' ratings in filter_movie_list.feature. You can use existing step definitions in web_steps.rb to check and uncheck the appropriate boxes, submit the form, and check whether the correct movies appear (you may ignore the case where the movie has no ratings).

Since it's tedious to repeat steps such as

When I check the 'PG' checkbox,
And I check the 'R' checkbox,
etc.

create a step definition to match a step such as:

Given I check the following ratings: G, PG, R

This single step definition should only check the specified boxes, and leave the other boxes as they were. Hint: This step definition can reuse existing steps in web_steps.rb, as shown in the example in Section 4.7 in ELLS.

For the scenario all ratings selected, it would be tedious to use "And I should see" to name every single movie. That would detract from the goal of BDD to convey the behavioral intent of the user story. To fix this, create step definitions in movie_steps.rb that will match steps of the form

Then I should see all of the movies

Hint: Consider counting the number of rows in the table to implement these steps. If you have computed rows as the number of table rows, you can use the assertion

rows.should == value

to fail the test in case the values don't match.

Use your new step definitions to complete the scenario all ratings selected. Success is when all scenarios in filter_movie_list.feature pass with all steps green.

Happy paths for sorting movies by title and by release date

Since the scenarios in sort_movie_list.feature involve sorting, you will need the ability to have steps that test whether one movie appears before another in the output listing. Create a step definition that matches a step such as "Then I should see 'Aladdin' before 'Amelie'."