Critical Business Logic Has No Test Coverage
Your test suite covers utility functions and simple CRUD operations but completely misses the critical business logic: payment processing, access control checks, data transformations, and state machine transitions. The parts of your code that are most likely to cause catastrophic failures if broken have zero test coverage.
Claude Code tends to generate tests for the easiest-to-test code (pure functions, simple helpers) while skipping the complex, stateful, integration-heavy code that actually needs testing the most. The coverage report may show 70% overall but the missing 30% contains all the high-risk logic.
This becomes painfully apparent when a 'small refactor' of the payment flow introduces a bug that charges customers the wrong amount, and no test catches it before production.
Error Messages You Might See
Common Causes
- Complex setup avoided — Tests for payment flows require Stripe test mode, database seeding, and multi-step setup that AI skips
- External service dependencies — Code that calls external APIs is left untested because mocking the API is complex
- State machine transitions untested — Status changes (pending -> processing -> completed -> failed) and their edge cases have no coverage
- Error handling paths untested — Only the happy path is tested; what happens on timeout, invalid input, or partial failure is unknown
- Coverage metrics misleading — Line coverage is high because simple code is tested, but branch coverage on critical paths is zero
How to Fix It
- Identify critical paths first — List your top 10 most important features (payment, auth, data export). These get tests first regardless of overall coverage
- Write integration tests for critical flows — Test the full flow from request to database, using test databases and service test modes (Stripe test keys)
- Test every state transition — For each status field, test every valid transition AND verify invalid transitions are rejected
- Test error handling explicitly — Force errors (network timeouts, invalid data, permission denied) and verify the app handles them gracefully
- Use branch coverage, not line coverage — Configure your coverage tool to report branch coverage. Aim for 100% branch coverage on critical paths
Real developers can help you.
Richard McSorley
Full-Stack Software Engineer with 8+ years building high-performance applications for enterprise clients. Shipped production systems at Walmart (4,000+ stores), Cigna (20M+ users), and Arkansas Blue Cross. 5 patents in retail/supply chain tech. Currently focused on AI integrations, automation tools, and TypeScript-first architectures.
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5 years+ Experienced Dev (Specially in Web Development), can help in python, javascript, react, next.js and full stack web dev technologies.
zipking
I am a technologist and product builder dedicated to creating high-impact solutions at the intersection of AI and specialized markets. Currently, I am focused on PropScan (EstateGuard), an AI-driven SaaS platform tailored for the Japanese real estate industry, and exploring the potential of Archify.
As an INFJ-T, I approach development with a "systems-thinking" mindset—balancing technical precision with a deep understanding of user needs. I particularly enjoy the challenge of architecting Vertical AI SaaS and optimizing Small Language Models (SLMs) to solve specific, real-world business problems. Whether I'm in a CTO-level leadership role or hands-on with the code, I thrive on building tools that turn complex data into actionable value.
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Anthony Akpan
Developer with 8 years of experience building softwares fro startups
Mehdi Ben Haddou
- Founder of Chessigma (1M+ users) & many small projects
- ex Founding Engineer @Uplane (YC F25)
- ex Software Engineer @Amazon and @Booking.com
Prakash Prajapati
I’m a Senior Python Developer specializing in building secure, scalable, and highly available systems. I work primarily with Python, Django, FastAPI, Docker, PostgreSQL, and modern AI tooling such as PydanticAI, focusing on clean architecture, strong design principles, and reliable DevOps practices. I enjoy solving complex engineering problems and designing systems that are maintainable, resilient, and built to scale.
Jaime Orts-Caroff
I'm a Senior Android developer, currently working at Aircall. I'm open to work in various fields!
Rudra Bhikadiya
I build and fix web apps across Next.js, Node.js, and DBs.
Comfortable jumping into messy code, broken APIs, and mysterious bugs.
If your project works in theory but not in reality, I help close that gap.
Sage Fulcher
Hey I'm Sage! Im a Boston area software engineer who grew up in South Florida. Ive worked at a ton of cool places like a telehealth kidney care startup that took part in a billion dollar merger (Cricket health/Interwell health), a boutique design agency where I got to work on a ton of exciting startups including a photography education app, a collegiate Esports league and more (Philosophie), a data analytics as a service startup in Cambridge (MA) as well as at Phillips and MIT Lincoln Lab where I designed and developed novel network security visualizations and analytics. I've been writing code and furiously devoted to using computers to make people’s lives easier for about 17 years. My degree is in making computers make pretty lights and sounds. Outside of work I love hip hop, the Celtics, professional wrestling, magic the gathering, photography, drumming, and guitars (both making and playing them)
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Get HelpFrequently Asked Questions
What should I test first when coverage is low?
Prioritize by risk: payment processing, authentication and authorization, data mutations that can't be undone, and any code that handles money or personal data. These are the paths where bugs cause the most damage.
How do I test code that calls external APIs?
Use the service's test mode (Stripe test keys, SendGrid sandbox) for integration tests. Use recorded HTTP responses (nock, VCR, responses) for unit tests. Test both success and error responses from the API.