How I Automatically Write Unit Tests for My Python Code Using GPT-4 and AST Parsing

Writing tests used to be a tedious afterthought — now, Python and GPT generate them for me based on my functions. No excuses left for skipping test coverage.

Zain Ahmad

4 min read

·

Jul 9, 2025

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I used to leave testing for last — or worse, skip it entirely. But with the help of Python’s AST module and GPT-4, I now generate entire test suites with a single command. This workflow not only saves hours but also helps maintain consistent test quality across all my projects. Let me show you how I built it — and how you can too.

1. Parse Python Code Using the AST Module

Before generating any test cases, I needed a way to extract all the functions from a .py file, including their names and arguments. Python’s built-in ast module makes this possible.

import ast
def extract_functions(filepath):
    with open(filepath, "r") as f:
        tree = ast.parse(f.read())
    functions = []
    for node in ast.walk(tree):
        if isinstance(node, ast.FunctionDef):
            functions.append({
                "name": node.name,
                "args": [arg.arg for arg in node.args.args]
            })
    return functions