Noting that jest also supports watch mode. (#1592)

Author: StevenInc

docs/guides/choosing-a-test-runner.md

@@ -6,7 +6,7 @@ There are many popular JavaScript test runners, and Vue Test Utils works with al
 
 There are a few things to consider when choosing a test runner though: feature set, performance, and support for single-file component (SFC) pre-compilation. After carefully comparing existing libraries, here are two test runners that we recommend:
 
-- [Jest](https://jestjs.io/docs/en/getting-started#content) is the most fully featured test runner. It requires the least configuration, sets up JSDOM by default, provides built-in assertions, and has a great command line user experience. However, you will need a preprocessor to be able to import SFC components in your tests. We have created the `vue-jest` preprocessor which can handle most common SFC features, but it currently does not have 100% feature parity with `vue-loader`.
+- [Jest](https://jestjs.io/docs/en/getting-started#content) is the most fully featured test runner. It requires the least configuration, sets up JSDOM by default, provides built-in assertions, and has a great command line user experience. However, you will need a preprocessor to be able to import SFC components in your tests. We have created the `vue-jest` preprocessor which can handle most common SFC features, but it currently does not have 100% feature parity with `vue-loader`. Jest also supports watch mode and watchAll.
 
 - [mocha-webpack](https://github.com/zinserjan/mocha-webpack) is a wrapper around webpack + Mocha, but with a more streamlined interface and watch mode. The benefits of this setup is that we can get complete SFC support via webpack + `vue-loader`, but it requires more configuration upfront.