beginner-testing

Testing & Quality

Introduce test-driven development to beginners with simple Flask/Sinatra test examples and TDD concepts

QUICK START

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Beginner Testing Introduction

Version: 0.17.0

When to Use

User's Vibe app ready to transition to Structured
User mentions "testing" or "how to test"
User has 3-4 features, wants quality assurance

Prerequisites

Working Flask/Sinatra app with 3-4 features
Understanding of routes and functions
Code works but no tests

What is Testing?

Without tests: Change code → Open browser → Click around → Hope nothing broke With tests: Change code → Run tests → See green/red → Know immediately

TDD Cycle

RED → GREEN → REFACTOR

1. RED: Write test that fails (feature doesn't exist)
2. GREEN: Write just enough code to pass
3. REFACTOR: Clean up while tests still pass

Test Types (Simple)

Type	Tests	Example
Unit	Individual functions	`add_numbers(2,3)` returns `5`
Route	Pages load correctly	`/` returns status 200
Integration	Parts work together	Form adds to database

Beginners: Start with route tests!

First Test (Flask)

# test_app.py
def test_homepage_loads():
    from app import app
    client = app.test_client()
    response = client.get('/')
    assert response.status_code == 200

Run: pip install pytest && pytest

First Test (Sinatra)

# test_app.rb
require 'minitest/autorun'
require 'rack/test'
require_relative 'app'

class AppTest < Minitest::Test
  include Rack::Test::Methods
  def app; Sinatra::Application; end

  def test_homepage_loads
    get '/'
    assert last_response.ok?
  end
end

Run: ruby test_app.rb

Common Assertions

Python: assert value == 5, assert 'text' in response.data Ruby: assert_equal 5, value, assert_includes body, 'text'

TDD Example: Delete Feature

# 1. RED - Write failing test
def test_delete_note():
    client = app.test_client()
    client.post('/add', data={'note': 'Test'})
    response = client.get('/delete/1')
    assert response.status_code == 302

# 2. GREEN - Make it pass
@app.route('/delete/<int:note_id>')
def delete_note(note_id):
    # implementation
    return redirect('/')

# 3. REFACTOR - Clean up

Test Output

Pass: 3 passed in 0.12s Fail: FAILED - AssertionError: assert 404 == 200

What to Test (Beginners)

Routes exist (not 404)
Forms submit successfully
Data saves/displays correctly

Common Mistakes

Mistake	Solution
Not running tests	Run after every change
Tests depend on order	Each test independent
One giant test	Small tests, one thing each

Benefits

Clarity: Test defines "working"
Confidence: Know when things break
Less fear: Change without worrying

End of Skill