cui-javascript-unit-testing

Jest unit testing standards define configuration for jsdom environment, babel-jest transforms, moduleNameMapper mocks for Lit and DevUI, and testMatch patterns. This ensures consistent test structure, proper mocking strategies, and 80% minimum coverage across branches, functions, lines, and statements in CI pipelines.

Standard Jest test structure uses testMatch patterns to locate tests, AAA (Arrange-Act-Assert) patterns for test logic, setupFiles for initialization, and consistent directory layouts. This approach keeps tests maintainable, discoverable, and aligned with project conventions.

Jest mocking strategies use moduleNameMapper to mock framework libraries like Lit and DevUI, and babel-jest for code transformation. These techniques isolate component tests from external dependencies, enabling faster test execution and predictable behavior.

Jest coverage management enforces an 80% global threshold across branches, functions, lines, and statements, with reports generated in text, lcov, html, and cobertura formats. This enables quality gates in CI pipelines and visibility into test coverage gaps.

Mocking is appropriate for unit tests isolating components and their immediate dependencies; integration testing combines multiple modules. Jest's mocking patterns focus on unit-level testing with controlled inputs, while integration tests validate end-to-end workflows across the stack.

Jest supports React and Lit-like component testing through jsdom testEnvironment, babel-jest transforms, and moduleNameMapper configuration for framework-specific mocks. This enables standardized unit testing across component libraries.