What is the difference between Unit, Integration, Regression, and Acceptance Testing?
I find it challenging to differentiate between these testing levels, especially when practicing TDD or unit testing. Can someone clearly explain regression testing vs unit testing, along with how and when to implement each of these testing types?
Unit Testing focuses on testing a single unit of code, usually a function or method. It’s a small, isolated test that ensures the smallest piece of your code works as expected. Unit tests are typically written using frameworks like RSpec or Minitest in Ruby.
Purpose: To verify that individual components of the code behave as expected.
When to use: Unit tests should be written for every function or method in your codebase. It’s generally the first layer of testing and the one used in TDD to drive the design of your software. Example: Testing a method that calculates tax:
def calculate_tax(amount)
amount * 0.05
end
RSpec.describe 'Tax Calculator' do
it 'calculates the correct tax amount' do
expect(calculate_tax(100)).to eq(5)
end
end
Integration Testing tests how different units or components of the system work together. While unit tests focus on individual methods or functions, integration tests ensure that multiple components function correctly when integrated.
Purpose: To check how different parts of the application interact, such as when one function calls another, or when data is passed between different modules.
When to use: After unit tests, integration tests are used to check if the components integrate well. Example: Testing if a controller, model, and view work together in a Rails app:
RSpec.describe 'User Registration' do
it 'creates a new user and redirects to the dashboard' do
post :create, params: { user: { name: 'Alice', email: 'alice@example.com' } }
expect(response).to redirect_to(dashboard_path)
end
end
Regression Testing ensures that new changes or features do not break existing functionality. It’s a type of testing that’s performed after code changes to verify that the new changes didn’t introduce any new bugs or break previously working features.
Purpose: To ensure that previously working code still functions after changes, whether it’s new features, bug fixes, or updates.
When to use: Every time you add a new feature, fix a bug, or make changes to the codebase. Regression tests should be run continuously to ensure the software maintains its stability.
Example: After updating a method to handle new requirements, regression testing would ensure that the existing functionality still works:
RSpec.describe 'Order Processing' do
it 'processes the order correctly even after adding a discount feature' do
expect(process_order(order)).to eq(expected_output)
end
end