1. 安装
yarn global add jest-cli or npm install -g jest-cli 备注：可以安装为依赖不用全局安装
2. 项目代码
a. 项目初始化yarn init -y ├── package.json├── sum.js├── sun.test.js└── yarn.lockb. package.json{ "name": "jestdemo", "version": "1.0.0", "main": "index.js", "license": "MIT", "dependencies": { "jest-cli": "^22.0.4" }, "scripts": { "test": "jest " }}c. sum.js（就是一个简单的sum 模块）module.exports=sum;function sum(a,b){ return a+b;}d. sum.test.js (按照约定 {name}.test.js 格式的是测试文件)const sum = require("./sum.js");describe("sum test suit", () => { test("test sum result", () => { expect(sum(1, 3)).toBe(4); }) test("appdemo", () => { expect(sum(1, 4)).toBeGreaterThan(2); })});e. 运行测试yarn run test结果PASS .\sum.test.js sum test suit √ test sum result (7ms) √ appdemo (2ms)Test Suites: 1 passed, 1 totalTests: 2 passed, 2 totalSnapshots: 0 totalTime: 1.443sRan all test suites.Done in 3.46s.f. 添加代码测试覆盖率修改package.json "scripts": { "test": "jest --watchAll --coverage" }界面：运行，如下图： 代码覆盖率如下图：
3. jest 命令行参数
Usage: jest.js [--config=] [TestPathPattern]Options: --help, -h Show help [boolean] --all The opposite of `onlyChanged`. If `onlyChanged` is set by default, running jest with `--all` will force Jest to run all tests instead of running only tests related to changed files. --automock Automock all files by default. [boolean] --bail, -b Exit the test suite immediately upon the first failing test. [boolean] --browser Respect the "browser" field in package.json when resolving modules. Some packages export different versions based on whether they are operating in node.js or a browser. [boolean] --cache Whether to use the transform cache. Disable the cache using --no-cache. [boolean] --cacheDirectory The directory where Jest should store its cached dependency information. [string] --changedFilesWithAncestor When used together with `--onlyChanged`, it runs tests related to the current changes and the changes made in the last commit. (NOTE: this only works for hg repos) [boolean] --ci Whether to run Jest in continuous integration (CI) mode. This option is on by default in most popular CI environments. It will prevent snapshots from being written unless explicitly requested. [boolean] [default: false] --clearCache Clears the configured Jest cache directory and then exits. Default directory can be found by calling jest --showConfig [boolean] --clearMocks Automatically clear mock calls and instances between every test. Equivalent to calling jest.clearAllMocks() between each test. [boolean] --collectCoverage Alias for --coverage. [boolean] --collectCoverageFrom relative to glob pattern matching the files that coverage info needs to be collected from. [string] --collectCoverageOnlyFrom Explicit list of paths coverage will be restricted to. [array] --color Forces test results output color highlighting (even if stdout is not a TTY). Set to false if you would like to have no colors. [boolean] --colors Alias for `--color`. [boolean] --config, -c The path to a jest config file specifying how to find and execute tests. If no rootDir is set in the config, the current directory is assumed to be the rootDir for the project. This can also be a JSON encoded value which Jest will use as configuration. [string] --coverage Indicates that test coverage information should be collected and reported in the output. [boolean] --coverageDirectory The directory where Jest should output its coverage files. [string] --coveragePathIgnorePatterns An array of regexp pattern strings that are matched against all file paths before executing the test. If the file pathmatches any of the patterns, coverage information will be skipped. [array] --coverageReporters A list of reporter names that Jest uses when writing coverage reports. Any istanbul reporter can be used. [array] --coverageThreshold A JSON string with which will be used to configure minimum threshold enforcement for coverage results [string] --debug Print debugging info about your jest config. [boolean] --detectLeaks **EXPERIMENTAL**: Detect memory leaks in tests. After executing a test, it will try to garbage collect the global object used, and fail if it was leaked [boolean] [default: false] --env The test environment used for all tests. This can point to any file or node module. Examples: `jsdom`, `node` or `path/to/my-environment.js` [string] --expand, -e Use this flag to show full diffs instead of a patch. [boolean] --findRelatedTests Find related tests for a list of source files that were passed in as arguments. Useful for pre-commit hook integration to run the minimal amount of tests necessary. [boolean] --forceExit Force Jest to exit after all tests have completed running. This is useful when resources set up by test code cannot be adequately cleaned up. [boolean] --globalSetup The path to a module that runs before All Tests. [string] --globalTeardown The path to a module that runs after All Tests. [string] --globals A JSON string with map of global variables that need to be available in all test environments. [string] --haste A JSON string with map of variables for the haste module system [string] --json Prints the test results in JSON. This mode will send all other test output and user messages to stderr. [boolean] --lastCommit Will run all tests affected by file changes in the last commit made. [boolean] --listTests Lists all tests Jest will run given the arguments and exits. Most useful in a CI system together with `--findRelatedTests` to determine the tests Jest will run based on specific files [boolean] [default: false] --logHeapUsage Logs the heap usage after every test. Useful to debug memory leaks. Use together with `--runInBand` and `--expose-gc` in node. [boolean] --mapCoverage Maps code coverage reports against original source code when transformers supply source maps. [boolean] --maxWorkers, -w Specifies the maximum number of workers the worker-pool will spawn for running tests. This defaults to the number of the cores available on your machine. (its usually best not to override this default) [number] --moduleDirectories An array of directory names to be searched recursively up from the requiring module's location. [array] --moduleFileExtensions An array of file extensions your modules use. If you require modules without specifying a file extension, these are the extensions Jest will look for. [array] --moduleNameMapper A JSON string with a map from regular expressions to module names that allow to stub out resources, like images or styles with a single module [string] --modulePathIgnorePatterns An array of regexp pattern strings that are matched against all module paths before those paths are to be considered "visible" to the module loader. [array] --modulePaths An alternative API to setting the NODE_PATH env variable, modulePaths is an array of absolute paths to additional locations to search when resolving modules. [array] --noStackTrace Disables stack trace in test results output [boolean] --notify Activates notifications for test results. [boolean] --onlyChanged, -o Attempts to identify which tests to run based on which files have changed in the current repository. Only works if you're running tests in a git repository at the moment. [boolean] --onlyFailures, -f Run tests that failed in the previous execution. [boolean] --outputFile Write test results to a file when the --json option is also specified. [string] --passWithNoTests Will not fail if no tests are found (for example while using `--testPathPattern`.) [boolean] [default: false] --preset A preset that is used as a base for Jest's configuration. [string] --projects A list of projects that use Jest to run all tests of all projects in a single instance of Jest. [array] --reporters A list of custom reporters for the test suite. [array] --resetMocks Automatically reset mock state between every test. Equivalent to calling jest.resetAllMocks() between each test. [boolean] --resetModules If enabled, the module registry for every test file will be reset before running each individual test. [boolean] --resolver A JSON string which allows the use of a custom resolver. [string] --rootDir The root directory that Jest should scan for tests and modules within. [string] --roots A list of paths to directories that Jest should use to search for files in. [array] --runInBand, -i Run all tests serially in the current process (rather than creating a worker pool of child processes that run tests). This is sometimes useful for debugging, but such use cases are pretty rare. [boolean] --runTestsByPath Used when provided patterns are exact file paths. This avoids converting them into a regular expression and matching it against every single file. [boolean] [default: false] --setupFiles The paths to modules that run some code to configure or set up the testing environment before each test. [array] --setupTestFrameworkScriptFile The path to a module that runs some code to configure or set up the testing framework before each test. [string] --showConfig Print your jest config and then exits. [boolean] --silent Prevent tests from printing messages through the console. [boolean] --snapshotSerializers A list of paths to snapshot serializer modules Jest should use for snapshot testing. [array] --testEnvironment Alias for --env [string] --testFailureExitCode Exit code of `jest` command if the test run failed [string] --testLocationInResults Add `location` information to the test results [boolean] [default: false] --testMatch The glob patterns Jest uses to detect test files. [array] --testNamePattern, -t Run only tests with a name that matches the regex pattern. [string] --testPathIgnorePatterns An array of regexp pattern strings that are matched against all test paths before executing the test. If the test path matches any of the patterns, it will be skipped. [array] --testPathPattern A regexp pattern string that is matched against all tests paths before executing the test. [array] --testRegex The regexp pattern Jest uses to detect test files. [string] --testResultsProcessor Allows the use of a custom results processor. This processor must be a node module that exports a function expecting as the first argument the result object [string] --testRunner Allows to specify a custom test runner. The default is `jasmine2`. A path to a custom test runner can be provided: ` /path/to/testRunner.js`. [string] --testURL This option sets the URL for the jsdom environment. [string] --timers Setting this value to fake allows the use of fake timers for functions such as setTimeout. [string] --transform A JSON string which maps from regular expressions to paths to transformers. [string] --transformIgnorePatterns An array of regexp pattern strings that are matched against all source file paths before transformation. [array] --unmockedModulePathPatterns An array of regexp pattern strings that are matched against all modules before the module loader will automatically return a mock for them. [array] --updateSnapshot, -u Use this flag to re-record snapshots. Can be used together with a test suite pattern or with `--testNamePattern` to re-record snapshot for test matching the pattern [boolean] --useStderr Divert all output to stderr. [boolean] --verbose Display individual test results with the test suite hierarchy. [boolean] --watch Watch files for changes and rerun tests related to changed files. If you want to re-run all tests when a file has changed, use the `--watchAll` option. [boolean] --watchAll Watch files for changes and rerun all tests. If you want to re-run only the tests related to the changed files, use the `--watch` option. [boolean] --watchPathIgnorePatterns An array of regexp pattern strings that are matched against all paths before trigger test re-run in watch mode. If the test path matches any of the patterns, it will be skipped. [array] --watchman Whether to use watchman for file crawling. Disable using --no-watchman. [boolean]Documentation: https://facebook.github.io/jest/Done in 0.69s.
4. 参考资料
https://facebook.github.io/jest/ https://github.com/rongfengliang/jestdemo
