Jest (https://jestjs.io/en/) ist eines (von mehreren) JavaScript Test Frameworks. Es unterstützt auch out-of-the-box code coverage (https://jestjs.io/docs/en/cli.html#coverage), d. h. hier ist nicht zwingend ein weiteres Tool notwendig.
Beispiel für jest.config.js (in unserem Fall mit ein paar Änderungen, weil wir webpack alias einsetzen und auch jest das verstehen sollte, das Standard-Verzeichnis für "coverage" geändert haben, etc.):
// For a detailed explanation regarding each configuration property, visit:
module.exports = {
// All imported modules in your tests should be mocked automatically
// automock: false,
// Stop running tests after `n` failures
// bail: 0,
// Respect "browser" field in package.json when resolving modules
// browser: false,
// The directory where Jest should store its cached dependency information
// cacheDirectory: "",
// Automatically clear mock calls and instances between every test
clearMocks: true,
// Indicates whether the coverage information should be collected while executing the test
//collectCoverage: true,
// An array of glob patterns indicating a set of files for which coverage information should be collected
//collectCoverageFrom: ["**/src/store/*.{js,jsx}", "!**/node_modules/**"],
//collectCoverageFrom: ["**/src/store/*.js"],
// The directory where Jest should output its coverage files
coverageDirectory: ".coverage",
// An array of regexp pattern strings used to skip coverage collection
// coveragePathIgnorePatterns: [
// "\\\\node_modules\\\\"
// ],
//A list of reporter names that Jest uses when writing coverage reports
// coverageReporters: [
// "json",
// "text",
// "lcov",
// //"clover"
// ],
// An object that configures minimum threshold enforcement for coverage results
// coverageThreshold: null,
// A path to a custom dependency extractor
// dependencyExtractor: null,
// Make calling deprecated APIs throw helpful error messages
// errorOnDeprecated: false,
// Force coverage collection from ignored files using an array of glob patterns
// forceCoverageMatch: [],
// A path to a module which exports an async function that is triggered once before all test suites
// globalSetup: null,
// A path to a module which exports an async function that is triggered once after all test suites
// globalTeardown: null,
// A set of global variables that need to be available in all test environments
// globals: {},
// An array of directory names to be searched recursively up from the requiring module's location
// moduleDirectories: [
// "node_modules"
// ],
// An array of file extensions your modules use
// moduleFileExtensions: [
// "js",
// "json",
// "jsx",
// "ts",
// "tsx",
// "node"
// ],
// A map from regular expressions to module names that allow to stub out resources with a single module
moduleNameMapper: {
"^components/(.*)$": "<rootDir>/src/components/$1",
"^backend/(.*)$": "<rootDir>/src/backend/$1",
"^constants/(.*)$": "<rootDir>/src/constants/$1",
"^entries/(.*)$": "<rootDir>/src/entries/$1",
"^pages/(.*)$": "<rootDir>/src/pages/$1",
"^store/(.*)$": "<rootDir>/src/store/$1",
"^types/(.*)$": "<rootDir>/src/types/$1",
"^utils/(.*)$": "<rootDir>/src/utils/$1",
},
// An array of regexp pattern strings, matched against all module paths before considered 'visible' to the module loader
// modulePathIgnorePatterns: [],
// Activates notifications for test results
// notify: false,
// An enum that specifies notification mode. Requires { notify: true }
// notifyMode: "failure-change",
// A preset that is used as a base for Jest's configuration
// preset: null,
// Run tests from one or more projects
// projects: null,
// Use this configuration option to add custom reporters to Jest
// reporters: undefined,
// Automatically reset mock state between every test
// resetMocks: false,
// Reset the module registry before running each individual test
// resetModules: false,
// A path to a custom resolver
// resolver: null,
// Automatically restore mock state between every test
// restoreMocks: false,
// The root directory that Jest should scan for tests and modules within
// rootDir: null,
// A list of paths to directories that Jest should use to search for files in
// roots: [
// "<rootDir>"
// ],
// Allows you to use a custom runner instead of Jest's default test runner
// runner: "jest-runner",
// The paths to modules that run some code to configure or set up the testing environment before each test
// setupFiles: [],
// A list of paths to modules that run some code to configure or set up the testing framework before each test
// setupFilesAfterEnv: [],
// A list of paths to snapshot serializer modules Jest should use for snapshot testing
// snapshotSerializers: [],
// The test environment that will be used for testing
testEnvironment: "node",
// Options that will be passed to the testEnvironment
// testEnvironmentOptions: {},
// Adds a location field to test results
// testLocationInResults: false,
// The glob patterns Jest uses to detect test files
//testMatch: ["**/__tests__/**/*.[jt]s?(x)", "**/?(*.)+(spec|test).[tj]s?(x)"],
// An array of regexp pattern strings that are matched against all test paths, matched tests are skipped
// testPathIgnorePatterns: [
// "\\\\node_modules\\\\"
// ],
// The regexp pattern or array of patterns that Jest uses to detect test files
// testRegex: [],
// This option allows the use of a custom results processor
// testResultsProcessor: null,
// This option allows use of a custom test runner
// testRunner: "jasmine2",
// This option sets the URL for the jsdom environment. It is reflected in properties such as location.href
// Setting this value to "fake" allows the use of fake timers for functions such as "setTimeout"
// timers: "real",
// A map from regular expressions to paths to transformers
// transform: null,
// An array of regexp pattern strings that are matched against all source file paths, matched files will skip transformation
// transformIgnorePatterns: [
// "\\\\node_modules\\\\"
// ],
// An array of regexp pattern strings that are matched against all modules before the module loader will automatically return a mock for them
// unmockedModulePathPatterns: undefined,
// Indicates whether each individual test should be reported during the run
verbose: false,
// An array of regexp patterns that are matched against all source file paths before re-running tests in watch mode
// watchPathIgnorePatterns: [],
// Whether to use watchman for file crawling
// watchman: true,
};
Das Plugin @babel/preset-env sollte bei "modules:auto" (default) beibehalten - webpack steuert Babel so, dass die (ES6) modules (imports) nicht transformiert (bzw. dann von webpack transformiert werden) - für jest (unter node) steuert Babel so, dass die (ES6) modules (imports) transformiert werden (weil node keine ES6 modules "versteht").
Wird useBuiltIns: "entry" verwendet , sollte auch targets gesetzt werden, weil ältere Versionen von node generator functions nicht verstehen.
Damit kann jest einmalig mit "npm test" auf der console gestartet werden.
Es gibt zahlreiche CLI Optionen (https://jestjs.io/docs/en/cli), z. B. kann man jest in einen watch mode versetzen und auch code coverage direkt ausgeben: