Fixture and factory usage in Ruby on Rails - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

What will be the user email after loading this fixture?

Given this YAML fixture for a User model, what will be the email of the user loaded in the test?

Ruby on Rails

users:
  one:
    id: 1
    name: "Alice"
    email: "[e-mail]"
  two:
    id: 2
    name: "Bob"
    email: "[e-mail]"

A "[e-mail]"

B "[e-mail]"

C "[e-mail]"

D nil

💡 Hint

Look at the fixture key used to load the user.

The fixture key 'one' corresponds to the user with email '[e-mail]'.

📝 Syntax

intermediate

Which factory definition is correct for a User with a dynamic email?

Choose the correct FactoryBot factory definition that creates a User with a unique email each time.

A

factory :user do
  email { "[e-mail]" }
  name { "Test User" }
end

B

factory :user do
  sequence(:email) { |n| "user#{n}@example.com" }
  name { "Test User" }
end

C

factory :user do
  email { generate(:email) }
  name { "Test User" }
end

D

factory :user do
  email { "user#{rand(100)}@example.com" }
  name { "Test User" }
end

💡 Hint

Look for the FactoryBot sequence syntax.

Option B uses FactoryBot's sequence to generate unique emails, which is the correct pattern.

🔧 Debug

advanced

Why does this test fail when using fixtures with associations?

Given these fixtures, why does the test fail with a 'nil' association error? users.yml: alice: id: 1 name: "Alice" posts.yml: first_post: id: 1 title: "Hello" user_id: 2

A The post fixture should use 'user' instead of 'user_id' for association.

B The fixtures are missing the 'created_at' timestamp causing failure.

C The post fixture references a user_id (2) that does not exist in users.yml.

D The user fixture 'alice' is not loaded because of a syntax error.

💡 Hint

Check the user_id value in posts.yml against users.yml ids.

The post references user_id 2, but users.yml only defines user with id 1, so the association is nil.

❓ state_output

advanced

What is the count of users after running this FactoryBot create sequence?

If you run this code in a test: 5.times { FactoryBot.create(:user) } What will User.count be?

A 5

B 1

C 0

D Error due to duplicate emails

💡 Hint

Assuming the factory uses sequences for unique emails.

Each create call adds one user, so after 5 calls, User.count is 5.

🧠 Conceptual

expert

Why prefer factories over fixtures in modern Rails testing?

Which reason best explains why many Rails developers prefer FactoryBot factories over fixtures?

A Fixtures load faster than factories, making tests run quicker.

B Factories require less code and no configuration compared to fixtures.

C Fixtures automatically handle complex associations better than factories.

D Factories allow dynamic, flexible data creation with traits and sequences, reducing brittle tests.

💡 Hint

Think about flexibility and test maintenance.

Factories provide dynamic data generation and traits, making tests easier to maintain and less fragile.