TDD in Legacy Code Outline

Legend

• ✅ Practical hands-on work (mandatory) - this includes Sandbox Project Tasks

• 📖 Supplementary reading (optional) - theory, concepts - you can read later

Setup Instructions

• ✅ Sandbox Project Setup

• 📖 Old Test Pyramid

• 📖 Modern Test Pyramid

• 📖 TDD Cycles

• 📖 Untestable Architecture

Phase 1. Pipeline in Legacy Code

• ✅ Commit Stage

• ✅ Release Stage

• ✅ Acceptance Stage

• 📖 Pipeline (Summary)

Phase 2. Acceptance Test Driven Development (ATDD) in Legacy Code

Smoke Tests

• ✅ E2E Testable Architecture

• 📖 Smoke Tests (Concepts)

• ✅ Smoke Tests

E2E Tests

• ✅ E2E Tests

• 📖 E2E Tests (Concepts)

• ✅ Maintainable E2E Tests

Acceptance Tests

• ✅ Acceptance Testable Architecture

• ✅ Acceptance Tests

• 📖 Acceptance Tests (Concepts)

• ✅ Maintainable Acceptance Tests

• ✅ External System Contract Tests

• 📖 External System Contract Tests (Concepts)

• ✅ Maintainable External System Contract Tests

Acceptance Test Driven Development (ATDD)

• ✅ Backlog Refinement

• ✅ ATDD - User Stories

• ✅ ATDD - User Stories - System DSL

• ✅ ATDD - User Stories - External System DSL

• ✅ ATDD - Bugs

• ✅ ATDD - System UI Redesign

• ✅ ATDD - System API Redesign

• ✅ ATDD - External System API Redesign

Further work on Legacy Code

• ✅ Comprehensive Acceptance Tests

• ✅ Comprehensive External System Contract Tests

Phase 3. Component Test Driven Development (CTDD) in Legacy Code

• ✅ Component Tests

• ✅ Maintainable Component Tests

• ✅ Contract Tests

• ✅ Test Driven Development (TDD)

Phase 4. Test Driven Development (TDD) in Legacy Code

• ✅ Hexagonal Architecture

• ✅ Unit Testing

• ✅ Narrow Integration Testing

• ✅ Test Driven Development (TDD)

• ✅ Code Coverage & Mutation Testing

• ✅ Static Code Analysis

Disclaimer: The series outline above is a rough draft. As I write the articles, I may update the outline (and may take into account reader feedback and questions).

Learn in practice

As a Premium Member, I will support you every step of the way.

This Series will provide you with rough guidance. However, as you try to apply it to your project, you may face additional challenges due to real-life complexities.

As a Premium Subscriber, I’ll be your mentor. As you read the series and try some steps, as you face roadblocks or challenges, you can ask me any questions by commenting on the article. Comments are only available to Premium Subscribers.

TDD in Legacy Code - Get Access

You tried TDD in your real-life project, but it didn’t work. You don’t want to waste years with trial-and-error. You don’t want to read hundreds of pages of books. That’s why I made the TDD in Legacy Code series:

✔ Step-by-step guide in introducing TDD to Legacy Code

✔ Applying the TDD transformation to Legacy Microservice Architecture

✔ Ask me questions about the challenges you face applying TDD in Legacy Code

TDD Sandbox Project Review

Membership Level

To get my review & feedback, you need to be a TDD Academy Member.

For new Members:

• 🔒Upgrade to premium (annual/monthly) plan to read premium articles, comment and ask questions

• 🔒Upgrade to the TDD Academy plan to get everything included in premium member and also get TDD Sandbox Project Review - I’ll review & provide feedback on your own Sandbox Project.

For existing Premium Members: As per my announcement about Updated Plans, if you’re a Premium Member (Annual/Monthly/Gift/Group Subscription) and had joined before 24th Jan 2025, then you will continue to have access to the TDD Sandbox Project Review until 31st Jan 2026 (next year). After that date, all Sandbox Project contributors will need to upgrade to TDD Academy Membership if they want to have continued access to TDD Sandbox Project Review.

Note: Before continuing, please read the TDD Sandbox Project Review for full details regarding membership levels (for individuals & teams) and the review process.

TDD Sandbox Project Dashboard

If you’ve commented on Substack with a link to your TDD Sandbox Project for me to review, you can see its status here: TDD Sandbox Project Dashboard.