Controller tests in Ruby on Rails - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to send a GET request to the index action in a Rails controller test.

Ruby on Rails

get [1]

Drag options to blanks, or click blank then click option'

Ausers_url

Bshow_url

Cedit_url

Dnew_url

Attempts:

3 left

💡 Hint

Common Mistakes

Using show_url instead of users_url

Using post instead of get

Forgetting to call the URL helper

In Rails controller tests, to test the index action, you send a GET request to users_url.

2fill in blank

medium

Complete the code to check that the response was successful in a Rails controller test.

Ruby on Rails

assert_response [1]

Drag options to blanks, or click blank then click option'

A:success

B:redirect

C:error

D:missing

Attempts:

3 left

💡 Hint

Common Mistakes

Using :redirect when expecting success

Using :error which means failure

Using :missing which means 404 not found

The assert_response :success checks that the HTTP response status is 200 OK.

3fill in blank

hard

Fix the error in the test code to correctly check that a new record was created after a POST request.

Ruby on Rails

assert_difference('[1].count', 1) do
  post users_url, params: { user: { name: 'Alice' } }
end

Drag options to blanks, or click blank then click option'

Auser

Busers

CUsers

DUser

Attempts:

3 left

💡 Hint

Common Mistakes

Using lowercase or plural names for the model

Using variable names instead of class names

The model class name User must be capitalized to check the count of records.

4fill in blank

hard

Fill both blanks to test that the show action renders successfully for a given user.

Ruby on Rails

get [1]([2])
assert_response :success

Drag options to blanks, or click blank then click option'

Auser_url

Buser

Cpost_url

Dpost

Attempts:

3 left

💡 Hint

Common Mistakes

Using post_url instead of user_url

Passing the model class instead of an instance

Use user_url to send the GET request and user to specify the user.

5fill in blank

hard

Fill all three blanks to test updating a user's name and checking the redirect.

Ruby on Rails

patch [1], params: { id: [2].id, user: { name: 'Bob' } }
assert_redirected_to [3]

Drag options to blanks, or click blank then click option'

Auser_url(user)

Buser

C:user

Dusers_url

Attempts:

3 left

💡 Hint

Common Mistakes

Using users_url instead of user_url(user)

Using symbol instead of URL helper for redirect

Passing class instead of instance for id

Use user_url(user) for the patch request URL, pass the user object for the id, and check redirect to user_url(user).

Practice

1. What is the main purpose of a controller test in Rails?

easy

A. To check if web requests respond correctly and perform expected actions

B. To test database schema changes

C. To verify CSS styles are applied properly

D. To check JavaScript functions run without errors

Solution

1. Step 1: Understand controller test role

   Controller tests simulate web requests to check if the controller responds correctly.

2. Step 2: Compare options

   Only To check if web requests respond correctly and perform expected actions describes checking web requests and expected actions, which is the controller test's purpose.

3. Final Answer:

   To check if web requests respond correctly and perform expected actions -> Option A

4. Quick Check:

   Controller tests check web requests = A [OK]

Hint: Controller tests simulate web requests to check responses [OK]

Common Mistakes:

• Confusing controller tests with database or view tests
• Thinking controller tests check CSS or JavaScript
• Assuming controller tests modify database schema

2. Which of the following is the correct syntax to simulate a GET request to the index action in a Rails controller test?

easy

A. get('/index')

B. get index

C. get index()

D. get :index

Solution

1. Step 1: Recall Rails controller test syntax

   In Rails controller tests, the correct way to simulate a GET request is using get :action_name.

2. Step 2: Analyze options

   get :index uses get :index, which is correct syntax. Others are invalid or incorrect Ruby syntax.

3. Final Answer:

   get :index -> Option D

4. Quick Check:

   Use symbol with get method = C [OK]

Hint: Use get :action_name with a symbol for controller tests [OK]

Common Mistakes:

• Using string or method call syntax instead of symbol
• Omitting colon before action name
• Using parentheses incorrectly

3. Given this controller test snippet:

get :show, params: { id: 1 }
assert_response :success
assert_not_nil assigns(:user)

What does assert_not_nil assigns(:user) check?

medium

A. That the @user variable was assigned in the controller

B. That the user with id 1 exists in the database

C. That the response body contains the word 'user'

D. That the controller redirected to the user page

Solution

1. Step 1: Understand assigns method in controller tests

   The assigns(:user) method accesses the instance variable @user set by the controller.

2. Step 2: Interpret assert_not_nil usage

   assert_not_nil assigns(:user) checks that @user is not nil, meaning it was assigned.

3. Final Answer:

   That the @user variable was assigned in the controller -> Option A

4. Quick Check:

   assigns(:user) checks @user variable = B [OK]

Hint: assigns(:var) checks controller instance variable @var [OK]

Common Mistakes:

• Thinking assigns checks database existence
• Confusing assigns with response content
• Assuming assigns checks redirects

4. Identify the error in this Rails controller test code:

post :create, user: { name: 'Alice' }
assert_redirected_to user_path(assigns(:user))

medium

A. assert_redirected_to should be assert_response

B. Using post instead of get for create action

C. Missing params: keyword before user hash in post request

D. assigns(:user) cannot be used in controller tests

Solution

1. Step 1: Check syntax for post request with parameters

   In Rails 5+, parameters must be wrapped inside params: keyword.

2. Step 2: Analyze given code

   The code uses post :create, user: { name: 'Alice' } missing params:, causing syntax error.

3. Final Answer:

   Missing params: keyword before user hash in post request -> Option C

4. Quick Check:

   Use params: for parameters in post requests = A [OK]

Hint: Always use params: keyword for request parameters [OK]

Common Mistakes:

• Omitting params: keyword in request methods
• Confusing HTTP verbs for actions
• Misusing assertion methods

5. You want to test that after creating a new user, the controller redirects to the user's show page and sets a flash notice. Which test code correctly checks both behaviors?

hard

A. post :create, params: { user: { name: 'Bob' } }
assert_response :redirect
assert_nil flash[:notice]

B. post :create, params: { user: { name: 'Bob' } }
assert_redirected_to user_path(assigns(:user))
assert_equal 'User created!', flash[:notice]

C. get :create, params: { user: { name: 'Bob' } }
assert_redirected_to user_path(assigns(:user))
assert flash[:alert] == 'User created!'

D. post :create, user: { name: 'Bob' }
assert_response :success
assert flash[:notice] == 'User created!'

Solution

1. Step 1: Check HTTP verb and parameters

   Creating a user uses POST with params: keyword, so post :create, params: { user: { name: 'Bob' } } assert_redirected_to user_path(assigns(:user)) assert_equal 'User created!', flash[:notice] is correct here.

2. Step 2: Verify assertions for redirect and flash

   post :create, params: { user: { name: 'Bob' } } assert_redirected_to user_path(assigns(:user)) assert_equal 'User created!', flash[:notice] asserts redirect to user's show page and flash notice equals 'User created!'. This matches the requirement.

3. Step 3: Eliminate incorrect options

   post :create, user: { name: 'Bob' } assert_response :success assert flash[:notice] == 'User created!' misses params: keyword and uses assert_response :success instead of redirect. get :create, params: { user: { name: 'Bob' } } assert_redirected_to user_path(assigns(:user)) assert flash[:alert] == 'User created!' uses GET instead of POST and wrong flash key. post :create, params: { user: { name: 'Bob' } } assert_response :redirect assert_nil flash[:notice] asserts flash[:notice] is nil, which is wrong.

4. Final Answer:

   post :create, params: { user: { name: 'Bob' } } assert_redirected_to user_path(assigns(:user)) assert_equal 'User created!', flash[:notice] -> Option B

5. Quick Check:

   POST with params, redirect, and flash notice = D [OK]

Hint: Use post with params:, assert_redirected_to, and assert_equal flash [OK]

Common Mistakes:

• Using get instead of post for create action
• Forgetting params: keyword
• Checking wrong flash key or missing redirect assertion