Security Testing
Authentication is the most critical security boundary in any web application. Broken authentication is consistently in the OWASP Top 10 because the implementation surface is enormous — JWTs, OAuth2 flows, session tokens, password reset flows, MFA. Each component can fail independently. This guide covers how to test each layer systematically. Key
Testing
Multi-agent systems (LangGraph workflows, CrewAI crews) are dramatically harder to test than single agents. State flows between agents, handoffs can fail silently, and emergent behaviors arise from agent interactions. This guide covers testing strategies for multi-agent orchestration: state validation, handoff testing, agent isolation, and failure injection. Single agents are hard
Testing
The .NET ecosystem has two mature approval/snapshot testing libraries: ApprovalTests.Net (the original) and Verify (the modern alternative with better async support and scrubbing). Both capture output to files and compare on subsequent runs. This guide covers both libraries with practical C# examples for NUnit and xUnit. Key Takeaways
Testing
Rate limiting in multi-tenant SaaS serves two goals: protecting infrastructure and enforcing plan limits. Both can break in ways that are hard to catch without explicit tests. The failure modes are distinct. Infrastructure protection fails when one tenant can starve other tenants — their traffic exhausts rate limit headroom that should
Testing
Billing bugs are the most expensive bugs in SaaS. A mishandled subscription upgrade that charges users incorrectly, a webhook that processes twice, or a dunning flow that locks out paying customers — each of these can generate support tickets, chargebacks, and churn that costs far more than the engineering time to
Testing
White-label SaaS is a forcing function for good multi-tenancy. When a customer runs your product under their own brand, on their own domain, with their own colors and logo, any configuration leak becomes immediately visible. Their customers see a broken experience with the wrong logo, wrong colors, or the wrong
Testing
Your onboarding flow is the most important user journey in your SaaS product. It's where first impressions form, where users decide whether your product is worth their time, and where the majority of churn is determined. Yet it's also where testing is most commonly neglected — teams
Testing
Feature flags in single-user apps are already tricky. In multi-tenant SaaS, they're an order of magnitude harder. You're not just controlling whether a feature is on or off — you're controlling which tenants see which features, often with different rollout percentages, different target rules, and
Testing
Data isolation bugs in multi-tenant SaaS are catastrophic. When tenant A can see tenant B's data, you don't get a bug report — you get a breach notification, a legal team, and customer churn. The failure mode is silent: everything looks fine until someone notices records they
Testing
WeasyPrint converts HTML/CSS to PDF in Python, making it popular for invoice generation, report rendering, and document exports in Django/Flask apps. Testing WeasyPrint output involves extracting text from the generated PDF bytes, comparing page structure, and doing visual regression checks against PNG renderings. This guide covers the full
Testing
LLM regressions are silent killers: the app still returns a response, but the quality degraded after a prompt change, model upgrade, or context window modification. Traditional regression tests that assert exact string equality fail immediately with LLMs. This guide covers behavioral regression testing, prompt versioning, LLM-as-judge evaluation, and CI gates
Testing
Apache PDFBox is an open-source Java library for reading and writing PDFs. Unlike iText (commercial license for production use), PDFBox is Apache-licensed. It's ideal for testing PDFs regardless of how they were generated — iText, wkhtmltopdf, Puppeteer, or any other tool. This guide shows how to parse, compare, and