如何进行angular的单元测试？

隔离程序的每个部件，在隔离环境中运行测试。这种测试形式叫作单元测试。在单元测试中，所写的测试需要事先提供既定的输入值与相应的逻辑单元，检测输出结果，确定它是否与我们的预期结果匹配。

下面来看一下Angular单元测试。

使用karma进行单元测试：

创建一个新的项目

ng new project --routing

运行ng test --help 可以看到测试相关的执行参数

options:
  --browsers
    Override which browsers tests are run against.
  --code-coverage
    Output a code coverage report.
  --code-coverage-exclude
    Globs to exclude from code coverage.
  --configuration (-c)
    A named configuration environment, as specified in the "configurations" section of angular.json.
  --environment
    Defines the build environment.
  --eval-source-map
    Output in-file eval sourcemaps.
  --help
    Shows a help message for this command in the console.
  --karma-config
    The name of the Karma configuration file.
  --main
    The name of the main entry-point file.
  --poll
    Enable and define the file watching poll time period in milliseconds.
  --polyfills
    The name of the polyfills file.
  --preserve-symlinks
    Do not use the real path when resolving modules.
  --prod
    When true, sets the build configuration to the production environment.
    All builds make use of bundling and limited tree-shaking, A production build also 
    runs limited dead code elimination using UglifyJS.
  --progress
    Log progress to the console while building.
  --reporters
    Karma reporters to use. Directly passed to the karma runner.
  --source-map
    Output sourcemaps.
  --ts-config
    The name of the TypeScript configuration file.
  --vendor-source-map
    Resolve vendor packages sourcemaps.
  --watch
    Run build when files change.

NO_ERRORS_SCHEMA告诉angular忽略那些不识别的元素或者元素属性.

--code-coverage -cc 代码覆盖率报告, 默认这个是不开启的, 因为生成报告的速度还是比较慢的.
--colors 输出结果使用各种颜色 默认开启
--single-run -sr 执行测试, 但是不检测文件变化 默认不开启
--progress 把测试的过程输出到控制台 默认开启
--sourcemaps -sm 生成sourcemaps 默认开启
--watch -w 运行测试一次, 并且检测变化 默认开启
ng test 就是运行测试, 并且如果文件有变化, 就会重新运行测试.

使用ng test -sr或者ng test -w false 执行单次测试

下面生成代码覆盖率报告: