Phase 0: The AI Code Quality Crisis · 40 min · Python · pytest · Hypothesis

Setting Up Your Testing Environment

Every tool in this course runs locally. Set them up once, use them for 55 labs.

Hiring signal: Engineers who can set up and configure a complete AI code testing toolchain demonstrate practical readiness -- they can start testing AI code on day one, not just talk about it theoretically. This is the minimum viable setup for the role.

What you will learn

Install and configure pytest, Hypothesis, mutmut, Semgrep, Ruff, and mypy
Set up pre-commit hooks for AI-generated code verification
Create the project scaffold that all 55 labs in this course depend on
Run a smoke test that verifies the entire toolchain is working

The Problem

Every lab in this course -- all 55 of them -- depends on a working testing toolchain. If you have to stop mid-lab to install a missing dependency or debug a configuration issue, you lose context and momentum. This lesson sets up the entire toolchain once, verifies it with a smoke test, and creates the project scaffold that every subsequent lab builds on.

The toolchain has six components, each corresponding to a layer of the verification pyramid:

Tool	Pyramid Layer	What it does
pytest	Unit	Runs unit tests
Hypothesis	Property-Based	Generates thousands of test inputs automatically
mutmut	Mutation	Mutates code to validate test quality
Semgrep	Security	Static analysis for CWE patterns
Ruff	Static Analysis	Fast Python linter
mypy	Static Analysis	Type checking

Plus pre-commit hooks to run them automatically on every commit.

Installation

Create a project directory and install all tools:

mkdir ai-code-testing && cd ai-code-testing
python -m venv .venv
source .venv/bin/activate
pip install pytest hypothesis mutmut semgrep ruff mypy pre-commit

Verify each tool is installed:

pytest --version
python -c "import hypothesis; print(hypothesis.__version__)"
mutmut --version
semgrep --version
ruff --version
mypy --version

Unlock the full lesson

You've read the first 2 sections. The rest of this lesson covers Project Scaffold, Configuration Files, Smoke Test, Build It — plus a hands-on lab, quiz, and project artifact.

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