Jest 20.0.0 发布了，Jest 是 Facebook 开源的无痛 JavaScript 测试工具。Jest 默认使用 Jasmine assertions，模块化，可扩展、可配置。Jest 也可以捕获 React 或其他可序列化值的快照，以便快速编写测试，并提供无缝的更新体验。
更新内容：
New
--projectsoption to run one instance of Jest in multiple projects at the same time.New multi project runner
New keyboard/arrow selection for watch mode typeaheads.
New --listTests flag.
New --showConfig flag.
New promise support for all
expectmatchers through.resolvesand.rejects.New
expect.hasAssertions()function similar toexpect.assertions().New
this.equalsfunction exposed to custom matchers.New
valid-expectlint rule ineslint-plugin-jest.New HtmlElement pretty-format plugin.
New Immutable pretty-format plugins.
New test environment per file setting through
@jest-environmentin the docblock.New feature that allows every configuration option to be set from the command line.
New feature to add custom reporters to Jest through
reportersin the configuration.New feature to add expected and actual values to AssertionError.
New feature to map code coverage from transformers.
New feature to run untested code coverage in parallel.
New option to define a custom resolver.
New printing support for text and comment nodes in html pretty-format.
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