Fixture and factory usage in Ruby on Rails - Step-by-Step Execution

Concept Flow - Fixture and factory usage

Start Test Setup

↓

Load Fixture Data

↓

Use Fixture in Test

↓

Run Test Assertions

↓

End Test

↓

Start Test Setup

↓

Call Factory to Build Object

↓

Use Factory Object in Test

↓

Run Test Assertions

↓

End Test

Tests start by either loading fixture data or calling a factory to create objects, then use these objects in tests before running assertions and ending.

Execution Sample

Ruby on Rails

test "user has valid email" do
  user = users(:one) # fixture
  assert user.email.include?('@')
end

This test uses a fixture named :one to get a user and checks if the email contains '@'.

Execution Table

Step	Action	Data Loaded/Created	Test Variable	Assertion Result
1	Load fixture users(:one)	User fixture data with email '[e-mail]'	user = users(:one)	N/A
2	Check if user.email includes '@'	N/A	user.email = '[e-mail]'	True
3	Assert condition	N/A	user.email.include?('@')	Pass
4	Test ends	N/A	N/A	Test Passed

💡 Test ends after assertion passes

Variable Tracker

Variable	Start	After Step 1	After Step 2	Final
user	nil	User object from fixture with email '[e-mail]'	Same	Same

Key Moments - 2 Insights

Why do we use fixtures instead of creating objects manually in tests?

Fixtures provide predefined data loaded before tests run, so tests can use consistent data without setup code, as shown in step 1 of the execution_table.

How is a factory different from a fixture in tests?

A factory creates objects dynamically during the test run, unlike fixtures which load static data before tests, allowing more flexible and customized test data.

Visual Quiz - 3 Questions

Look at the execution_table, what is the value of 'user.email' after step 2?

A '[e-mail]'

B '[e-mail]'

C nil

D 'noemail'

💡 Hint

Check the 'Test Variable' column at step 2 in the execution_table.

At which step does the test check if the email contains '@'?

A Step 1

B Step 2

C Step 3

D Step 4

💡 Hint

Look at the 'Action' column in the execution_table for the condition check.

If we replaced the fixture with a factory that creates a user with email '[e-mail]', what changes in the variable_tracker?

A The 'user' variable would be nil throughout

B The 'user' variable would have email '[e-mail]' after step 1

C The 'user' variable would have email '[e-mail]' after step 1

D No change in 'user' variable

💡 Hint

Consider how factories create objects dynamically compared to fixtures.

Concept Snapshot

Fixtures load static test data before tests run.
Factories create test objects dynamically during tests.
Use fixtures for simple, consistent data.
Use factories for flexible, customized data.
In tests, access fixtures by name (e.g., users(:one)).
Factories are called as methods to build objects.

Full Transcript

In Rails testing, fixtures and factories help create test data. Fixtures are predefined data loaded before tests, accessible by names like users(:one). Factories build objects dynamically during tests, allowing more customization. Tests use these objects to check behavior, like verifying a user's email contains '@'. The execution flow starts with loading or creating data, then running assertions, and finally ending the test. Understanding when and how data is prepared helps write clear and reliable tests.