Testing Error Paths
Test failures and edge inputs deliberately, assert the error type and message, and stop the happy path from hiding bugs.
~2 min readread →
Developer interview notes & guides — Page 11
Focused explanations and longer guides, with worked scenarios, common mistakes and interview exercises across every chapter.
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Showing 241–264 of 825 articles
Unit and Integration Test Balance
Separate fast isolated unit tests from integration tests that use real dependencies, and find the balance that catches real bugs.
~2 min readread →
Parallel Test Isolation
Run tests in parallel without interfering by removing shared state, isolating resources, and randomizing order.
~2 min readread →
Red, Green, Refactor
Write a failing test first, make it pass minimally, then refactor under green, and understand why the order matters.
~2 min readread →
Snapshot Tests Worth Reviewing
Keep snapshots small and intentional, review every diff, and stop large snapshots from becoming rubber-stamped assertions.
~2 min readread →
Test Data Builders and Object Mothers
Build valid test objects with defaults and override only what a test cares about, to keep tests readable and robust.
~2 min readread →
TypeScript Abstract Classes and Contracts
Share behavior with abstract classes, enforce required members, and decide when an interface or composition is the better contract.
~2 min readread →
TypeScript Declaration Files and Untyped Packages
Write .d.ts files for JavaScript packages, declare modules, and expose types with the package.json types field.
~2 min readread →
TypeScript Enums vs Union Types
Compare enums with unions of string literals: runtime cost, serialization, exhaustiveness and which one fits application code.
~3 min readread →
TypeScript Generic Defaults and Parameter Order
Give type parameters defaults to make them optional, and order them so inference still works without explicit arguments.
~2 min readread →
TypeScript Index Signatures and Constraints
Model keyed collections with index signatures, type the value side, and avoid the loose any that hides real type errors.
~3 min readread →
TypeScript Key Remapping in Mapped Types
Rename mapped-type keys with an as clause, filter keys by mapping to never, and build getter and prefixed types generically.
~2 min readread →
TypeScript Strict Compiler Flags
Turn on strict checks, know which flags strict bundles, and layer the non-strict extras such as noUncheckedIndexedAccess.
~2 min readread →
TypeScript Template Literal Types
Compose string types with template literals, interpolate unions to generate combinations, and understand how they stay type-level only.
~2 min readread →
TypeScript this Types and Fluent APIs
Use polymorphic this return types for builders, keep chaining correct through subclasses, and constrain this parameters.
~2 min readread →
Can't bind to 'ngModel' since it isn't a known property of 'input' in Angular
Fix Angular NG8002 Can't bind to 'ngModel' since it isn't a known property of 'input': import FormsModule, then fix formControl and inputs.
~7 min readread →
Angular 'Blocked by CORS Policy' on ng serve: Fix with proxy.conf.json
Fix 'blocked by CORS policy' errors when Angular ng serve calls a backend: proxy.conf.json, angular.json wiring and production CORS setup.
~7 min readread →
ExpressionChangedAfterItHasBeenCheckedError in Angular (NG0100)
Fix Angular NG0100 ExpressionChangedAfterItHasBeenCheckedError: why the dev-mode check fires, and data-flow fixes that beat setTimeout.
~8 min readread →
'app-x' is not a known element in Angular (NG8001): How to Fix It
Fix Angular NG8001 'app-x' is not a known element: standalone imports, selector typos, NgModule exports, schemas and TestBed setup.
~7 min readread →
NullInjectorError: No provider for X! in Angular (NG0201): How to Fix
Fix Angular NullInjectorError: No provider for X! (NG0201): read the injector path, add provideHttpClient(), providedIn root or a token.
~7 min readread →
Docker Container Exits Immediately: How to Debug It
Why a Docker container exits immediately: check the exit code, read docker logs, open a shell and fix a command that only starts a background job.
~5 min readread →
Docker 'exec format error': When the Image CPU Does Not Match
Fix 'exec format error' in Docker: confirm the CPU architecture mismatch with uname and docker inspect, then rebuild with the right --platform or buildx target.
~6 min readread →
Docker 'no space left on device': Safe Cleanup for Builds and Pulls
Fix Docker 'no space left on device' during build or pull: measure with docker system df, prune in a safe order, and cap logs and build cache.
~8 min readread →
Docker permission denied on /var/run/docker.sock: Fixes and Risks
Fix 'permission denied while trying to connect to the Docker daemon socket': docker group, re-login, rootless mode, contexts and a dead daemon.
~8 min readread →
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