Week 7 Lab — Software Testing

CSCI 4250 Software Engineering 1

Welcome to the lab. You will build and run tests for a small order management system in three structured steps.

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Quick Start

1. Open this folder in VS Code (File → Open Folder → select this folder)
2. Open a terminal: Ctrl + `` ``
3. Install pytest: pip install pytest
4. Configure tests: Ctrl+Shift+P → Python: Configure Tests → pytest → .
5. Follow the instructions below in order

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The System Under Test

Five Python modules that work together:

src/
├── inventory.py      — tracks stock levels (get_stock, reduce_stock)
├── orders.py         — processes a single order (place_order)
├── notifications.py  — sends confirmation messages (send_confirmation)
├── cart.py           — manages a customer's shopping cart (add_to_cart, checkout)
└── checkout.py       — the "Place Order" feature (checkout) — coordinates all others

The dependency chain is:

checkout.py  →  cart.py
checkout.py  →  orders.py  →  inventory.py
                orders.py  →  notifications.py

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Lab Steps — Do These in Order

Step	File	What you are learning
Step 1	instructions/STEP1_INSTRUCTIONS.md	Unit testing — test each module in isolation with mocks
Step 2	instructions/STEP2_INSTRUCTIONS.md	Feature testing — test a complete user-facing feature end-to-end
Step 3	instructions/STEP3_INSTRUCTIONS.md	Integration testing — wire all modules together, introduce a bug, watch it get caught
Step 4	instructions/STEP4_INSTRUCTIONS.md	System testing — discussion of what lower levels cannot catch

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Running Tests (Quick Reference)

Open the VS Code terminal and use these commands from the project root.

Step 1 — Unit tests only:

pytest tests/test_step1_unit_inventory.py tests/test_step1_unit_orders.py -v

Step 2 — Feature tests only:

pytest tests/test_step2_feature.py -v

Step 3 — Integration tests only:

pytest tests/test_step3_integration.py -v

Run everything at once:

pytest -v

Run with a short summary at the end:

pytest -v --tb=short

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Reading Test Output

PASSED   — test ran and all assertions passed ✅
FAILED   — test ran but an assertion was wrong ❌
ERROR    — test could not even start (usually an import error)

When a test fails, pytest shows you:

• The file and line number
• The assertion that failed
• The actual value vs the expected value

Example:

AssertionError: assert 0 == 7
  Left:  actual result
  Right: what we expected

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VS Code Test Explorer

Click the beaker icon (🧪) in the left sidebar to open the Test Explorer. From there you can:

• See all tests organised by file and class
• Run individual tests by clicking ▶ next to them
• See pass/fail status with colour coding
• Click a failed test to jump straight to the failing line

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Folder Structure

lab/
├── README.md                             ← you are here
├── conftest.py                           ← path setup (do not edit)
├── src/
│   ├── inventory.py
│   ├── orders.py
│   ├── notifications.py
│   ├── cart.py                           ← added in Step 2
│   └── checkout.py                       ← added in Step 2
├── tests/
│   ├── test_step1_unit_inventory.py      ← Step 1
│   ├── test_step1_unit_orders.py         ← Step 1
│   ├── test_step2_feature.py             ← Step 2
│   └── test_step3_integration.py         ← Step 3
└── instructions/
    ├── STEP1_INSTRUCTIONS.md
    ├── STEP2_INSTRUCTIONS.md
    ├── STEP3_INSTRUCTIONS.md
    └── STEP4_INSTRUCTIONS.md

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If Something Goes Wrong

Problem	Fix
ModuleNotFoundError: No module named 'inventory'	Make sure you opened the lab/ folder in VS Code, not a subfolder. conftest.py must be in the root.
ModuleNotFoundError: No module named 'pytest'	Run pip install pytest in the terminal
Tests don't appear in the beaker panel	Ctrl+Shift+P → Python: Configure Tests → pytest → .
VS Code is using the wrong Python	Ctrl+Shift+P → Python: Select Interpreter → choose Python 3.x
pytest command not found	Try python -m pytest -v instead