Python
Reproducibility is the foundation of scientific computing. A notebook that produces a result should produce the same result when re-executed—same inputs, same code, same environment. nbval enforces this by re-running a notebook and comparing each cell's output to the recorded output in the .ipynb file. Any difference
Python
nbmake is a pytest plugin that treats Jupyter notebooks as test cases. Install it, point pytest at a directory of notebooks, and every notebook that executes without error passes. Every notebook that raises an exception fails. It is the simplest possible notebook testing setup, and for most teams it is
Python
Jupyter notebooks are the primary artifact for data science work—model training, data exploration, report generation. Yet most teams treat them as write-only documents. Notebooks break silently when dependencies update, when data shapes change, or when code paths that ran during development are skipped during the final run. Testing notebooks
Internationalization
Vue applications using vue-i18n face a common testing problem: the i18n plugin must be configured and installed before any component that uses $t() or useI18n() can render. Without the right setup, tests fail with "inject() can only be used inside setup()" or "Cannot read properties of undefined&
Internationalization
react-intl is the standard i18n library for React applications built on the FormatJS ecosystem. Testing it well means more than verifying that text appears—it means asserting that the correct translation appears, that pluralization rules are respected, and that date and number formatting matches locale expectations. This guide covers the
Internationalization
Internationalization testing is one of those areas that teams defer until a customer reports that dates are backwards or buttons overflow in German. By then, the cost of fixing it is much higher than getting ahead of it. This guide covers the fundamentals of i18n testing across the three most
Internationalization
Angular's approach to internationalization creates a testing challenge: the default compile-time i18n bakes translations into the build, making runtime locale switching in unit tests awkward. This guide covers how to configure Angular TestBed for locale-aware testing, how to unit test locale-sensitive pipes, and how to use component harnesses
Internationalization
Unit tests verify that translation keys are correct; end-to-end tests verify that the application actually delivers the right experience when a real user visits with a specific locale. Playwright's projects configuration makes multi-locale E2E testing practical—you define locale-specific configurations once and the entire test suite runs against
Python
Papermill is a tool for parameterizing and executing Jupyter notebooks programmatically. It was designed for production notebook workflows—running the same analysis against different datasets, date ranges, or configuration sets—but it also makes notebooks significantly more testable. By injecting parameters and capturing outputs, you can test a notebook against
Internationalization
Right-to-left language support is one of the most visually complex parts of internationalization. When a user switches to Arabic or Hebrew, the entire layout must mirror: navigation moves from right to left, text alignment flips, icons with directional meaning reverse, and form inputs realign. Testing this requires a different mindset
Chaos Engineering
Toxiproxy sits between your application and a downstream service and injects network problems: latency, bandwidth limits, dropped connections, slow responses, and timeouts. Unlike infrastructure-level chaos tools, Toxiproxy works at the TCP level and is easy to control programmatically — making it ideal for integration tests that need to verify how your
API Testing
Schemathesis and Dredd both test APIs against their OpenAPI specifications. They're often mentioned in the same breath, which leads teams to think they're interchangeable. They're not. They find different bugs, in different ways, with different tradeoffs. Understanding the distinction helps you deploy the right