FastAPI Calculator — Midterm Project

A full-stack calculator application built with FastAPI and tested with unit, integration, and end-to-end (Playwright) tests. Includes structured logging and a GitHub Actions CI pipeline.

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Features

• Web UI — browser-based calculator with live results and history table
• REST API — JSON endpoints for all arithmetic operations
• 10 operations — addition, subtraction, multiplication, division, power, root, modulus, integer division, percent, absolute difference
• Logging — all requests and errors logged to data/logs/fastapi_calculator.log
• 81 tests — unit, integration, and end-to-end
• GitHub Actions CI — runs all tests automatically on every push

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Project Structure

Midterm_Project-main/
├── fastapi_app.py              # FastAPI application (routes + logging)
├── templates/
│   └── index.html              # Web UI (HTML + JavaScript)
├── app/
│   ├── operations.py           # All math operation classes + factory
│   ├── calculation.py          # Calculator facade
│   ├── calculator_repl.py      # Original CLI REPL interface
│   ├── exceptions.py           # Custom exception classes
│   └── ...                     # Config, history, commands, observers
├── tests/
│   ├── test_unit_operations.py     # Unit tests for operations.py
│   ├── test_integration_api.py     # Integration tests for API endpoints
│   ├── test_e2e_playwright.py      # End-to-end browser tests
│   └── ...                         # Original CLI test suite
├── conftest.py                 # Shared pytest fixtures (live server)
├── .github/workflows/ci.yml    # GitHub Actions CI workflow
├── requirements.txt
└── pytest.ini

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Supported Operations

Operation	API name	Example
Addition	add	5 + 3 = 8
Subtraction	sub	10 − 4 = 6
Multiplication	mul	6 × 7 = 42
Division	div	20 ÷ 4 = 5
Power	pow	2 ^ 10 = 1024
Root	root	∛27 = 3
Modulus	mod	10 % 3 = 1
Integer Division	int_divide	10 // 3 = 3
Percentage	percent	(50/200)×100 = 25%
Absolute Difference	abs_diff	|3 − 10| = 7

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Installation

1. Clone the repository

git clone <your-repository-url>
cd Midterm_Project-main

2. Create and activate a virtual environment

python -m venv .venv

# Windows
.venv\Scripts\activate

# Mac/Linux
source .venv/bin/activate

3. Install dependencies

pip install -r requirements.txt

4. Install Playwright browser

playwright install chromium

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Running the Web Application

uvicorn fastapi_app:app --reload

Open http://127.0.0.1:8000 in your browser.

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API Endpoints

Method	Endpoint	Description
GET	/	Calculator web UI
POST	/calculate	Perform a calculation (form data: operation, a, b)
GET	/history	Retrieve calculation history (JSON)
DELETE	/history	Clear calculation history
GET	/operations	List all supported operation names
GET	/health	Health check

Example — POST /calculate

curl -X POST http://127.0.0.1:8000/calculate \
  -d "operation=add&a=5&b=3"

{"result": 8.0, "operation": "add", "a": 5.0, "b": 3.0}

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Running Tests

Unit + Integration tests

python -m pytest tests/test_unit_operations.py tests/test_integration_api.py -v

End-to-End tests (requires the browser)

python -m pytest tests/test_e2e_playwright.py -v --browser chromium

All new tests together

python -m pytest tests/test_unit_operations.py tests/test_integration_api.py tests/test_e2e_playwright.py -v --browser chromium

Run with coverage

pytest --cov=app --cov-report=term-missing

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Test Summary

Test file	Type	Tests
test_unit_operations.py	Unit	43
test_integration_api.py	Integration	25
test_e2e_playwright.py	End-to-End	13
Total		81

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Logging

All operations and errors are logged to:

data/logs/fastapi_calculator.log

Log format:

2025-01-01 12:00:00 | INFO | Calculation request: 5.0 add 3.0
2025-01-01 12:00:00 | INFO | Result: 5.0 add 3.0 = 8.0

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Continuous Integration

GitHub Actions runs all three test suites automatically on every push or pull request to main/master.

Workflow file: .github/workflows/ci.yml

Steps:

1. Checkout repository
2. Set up Python 3.11
3. Install dependencies
4. Install Playwright Chromium browser
5. Run unit tests
6. Run integration tests
7. Run end-to-end tests

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Design Patterns (CLI Calculator)

The underlying calculator library (app/) demonstrates several design patterns:

Pattern	Where used
Factory	OperationFactory — creates operation instances by name
Facade	CalculatorFacade — unified interface over history, memento, observers
Command	commands.py — each REPL action is an encapsulated command object
Observer	observers.py — logging and auto-save observers
Memento	calculator_memento.py — undo/redo state management
Decorator	@OperationFactory.register(...) — registers operations at class definition

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Author

Isha Jagtap
Master's in Computer Science — NJIT