Test doubles concept in Ruby - Mini Project: Build & Apply

Test doubles concept

📖 Scenario: You are writing tests for a simple Ruby class that sends messages. Sometimes, you want to test your code without actually sending messages. To do this, you use a test double, which acts like a fake message sender.

🎯 Goal: Learn how to create and use a test double in Ruby to simulate a message sender in tests.

📋 What You'll Learn

Create a test double named fake_sender

Set up the test double to respond to send_message method

Call send_message on the test double with a specific message

Print the result of calling send_message on the test double

💡 Why This Matters

🌍 Real World

Test doubles help developers test parts of their code without relying on real objects, which might be slow, unavailable, or have side effects.

💼 Career

Understanding test doubles is important for writing effective automated tests in software development jobs, improving code quality and reliability.

1

Create a test double named fake_sender

Write a line of Ruby code to create a test double called fake_sender using double.

Ruby

# Create a test double named fake_sender
# Your code here

Need a hint?

Use double('Name') to create a test double in Ruby.

2

Set up fake_sender to respond to send_message

Write a line of Ruby code to make fake_sender respond to send_message with the string 'Message sent'.

Ruby

fake_sender = double('MessageSender')
# Make fake_sender respond to send_message
# Your code here

Need a hint?

Use allow(double).to receive(:method).and_return(value) to set the response of a test double method.

3

Call send_message on fake_sender with a message

Write a line of Ruby code to call send_message on fake_sender with the argument 'Hello!' and save the result in a variable called result.

Ruby

fake_sender = double('MessageSender')
allow(fake_sender).to receive(:send_message).and_return('Message sent')
# Call send_message on fake_sender with 'Hello!'
# Your code here

Need a hint?

Call the method on the test double and assign the return value to result.

4

Print the result of calling send_message

Write a line of Ruby code to print the value of the variable result.

Ruby

fake_sender = double('MessageSender')
allow(fake_sender).to receive(:send_message).and_return('Message sent')
result = fake_sender.send_message('Hello!')
# Print the result
# Your code here

Need a hint?

Use puts result to print the value.