chore(doc): write testing tips in README.md

README.md

@@ -530,6 +530,22 @@ Also, the `args` option is passed to the browser instance. List of Chromium flag
 HCCrawler.launch({ args: ['--disable-web-security'] });
 ```
 
+### Running tests
+
+All tests but RedisCache's are run by the following command.
+
+```sh
+yarn test
+```
+
+When you modify [RedisCache](https://github.com/yujiosaka/headless-chrome-crawler/blob/master/cache/redis.js)'s code, its tests are run by the following comannd:
+
+```sh
+yarn test-all
+```
+
+Make sure that [Redis](https://redis.io/) is installed and its server is started.
+
 ### Enable debug logging
 
 All requests and browser's logs are logged via the [debug](https://github.com/visionmedia/debug) module under the `hccrawler` namespace.