Claude Code vs GitHub Copilot

Write unit tests for the untested modules in this codebase. Start by running the existing test command with coverage to find the gaps, then prioritize pure logic: parsers, formatters, price or date calculations, permission checks. For each target module write cases for the documented behavior, boundary inputs (empty arrays, zero, negative numbers, unicode strings), and the error paths that throw or return early. Mock only true externals like network and filesystem; do not mock the module under test's own collaborators unless construction is impractical. Match the assertion style already used in the repo. Skip snapshot tests unless one already exists for that area. After writing each file, run it in isolation, then run the whole suite to confirm nothing else broke. Finish with a short table: module, cases added, and uncovered branches that still remain with the reason.

Write unit tests for the module I have open in the editor. First read the file and list its exported functions, the branches inside each, and any external calls that need mocking, then generate the test file next to it following the naming pattern the repo already uses. Cover each branch, not just the happy path: boundary values, empty inputs, thrown errors from mocked dependencies, and any async rejection paths. Mock at module boundaries only; do not mock the function under test or private helpers. Use the assertion style and test runner already configured in the project rather than introducing a new one. If a function is untestable without refactoring, say so and stop instead of testing implementation details. Run the new tests, confirm they pass, then deliberately break one assertion to prove the test can fail, and restore it.

Migrate this JavaScript codebase to TypeScript incrementally, keeping the app buildable after every step. First add tsconfig.json with allowJs and checkJs enabled and strict off, run the compiler, and report the baseline error count. Then convert files in dependency order, leaf modules first: rename with git mv so history survives, add explicit types for exported functions, and use unknown instead of any at module boundaries. Do not change runtime behavior; if a bug surfaces during typing, note it in a TODO comment instead of fixing it silently. After each batch of ten files, run tsc and the existing test suite and stop if either fails. Once every file is converted, turn on strict, fix what breaks, and give me the final tsc output plus a list of any remaining any types with file and line.

Migrate this package from JavaScript to TypeScript one directory at a time, starting with src/utils because nothing imports it from outside. First add tsconfig.json with allowJs true, checkJs false, and strict true so converted files are held to the full standard while the rest compiles untouched. Rename each file to .ts, type exported function signatures explicitly, and let inference handle locals. Where a shape crosses module boundaries, lift it into src/types.ts rather than repeating inline object types. Do not change any runtime behavior, no logic edits, no reordering, and flag any spot where an implicit any hides a probable bug instead of silently casting. Never use ts-ignore, prefer unknown plus a narrowing check. After each directory, I will run npx tsc --noEmit and the existing test suite, and the diff must show only renames and type annotations.