RSpec expectations and matchers in Ruby - Mini Project: Build & Apply

RSpec Expectations and Matchers

📖 Scenario: You are writing tests for a simple Ruby method that calculates the square of a number. Testing helps you check if your code works as expected before using it in real projects.

🎯 Goal: Build a basic RSpec test suite using expectations and matchers to verify that a square method returns correct results for given inputs.

📋 What You'll Learn

Create a Ruby method called square that returns the square of a number

Write an RSpec test file with a describe block for the square method

Use expect with the eq matcher to check the output for input 3

Add a test using the be_a matcher to confirm the output is an Integer

Use the not_to matcher to verify the output is not zero for input 5

💡 Why This Matters

🌍 Real World

Testing code with RSpec is common in Ruby projects to catch bugs early and ensure code quality.

💼 Career

Many Ruby developer jobs require writing and understanding RSpec tests to maintain reliable software.

1

Create the square method

Write a Ruby method called square that takes one parameter n and returns n * n.

Ruby

# Your code here

Need a hint?

Define a method with def and return the number multiplied by itself.

2

Set up RSpec describe block

Write an RSpec describe block for the square method. Inside it, write an it block with description 'returns the square of a number'.

Ruby

def square(n)
  n * n
end

# Your code here

Need a hint?

Use RSpec.describe 'square' do and inside it an it block with the given description.

3

Add expectation with eq matcher

Inside the it block, write an expectation using expect(square(3)) and the eq(9) matcher to check the output.

Ruby

def square(n)
  n * n
end

RSpec.describe 'square' do
  it 'returns the square of a number' do
    # Your code here
  end
end

Need a hint?

Use expect with the method call and to eq(9) to check the result.

4

Add more matchers and print test results

Add two more tests inside the describe block: one using expect(square(4)).to be_a(Integer) to check the output type, and another using expect(square(5)).not_to eq(0) to confirm the output is not zero. Then run the tests to see the results.

Ruby

def square(n)
  n * n
end

RSpec.describe 'square' do
  it 'returns the square of a number' do
    expect(square(3)).to eq(9)
  end

  # Your code here
end

Need a hint?

Use be_a(Integer) matcher to check type and not_to eq(0) to check value is not zero.