Update README.

README.md

@@ -144,13 +144,26 @@ on Google Cloud Platform.
 
         npm install
 
+    or
+
+        yarn install
+
 1. Run the sample:
 
         node sample_file.js [args]...
 
 ### How to run the tests
 
 1. Read the [Contributing Guide][contrib].
+1. You must install dependencies at the root of the `nodejs-docs-samples`
+directory. You can do so with `yarn` or `npm`:
+
+        npm install
+
+    or
+
+        yarn install
+
 1. In a terminal, start Redis:
 
         redis-server
@@ -163,22 +176,81 @@ on Google Cloud Platform.
 
         npm test
 
-    or with coverage:
+    or
+
+        yarn test
+
+    With code coverage:
+
+        npm run cover
+
+    or
 
-        npm run coverage
+        yarn run cover
 
 1. Then run the system tests from the root of the project:
 
         npm run system-test
 
-    or with coverage:
+    or
+
+        yarn run system-test
+
+    With code coverage:
 
         npm run system-cover
 
-1. Or run all the tests at once with coverage:
+    or
+
+        yarn run system-cover
+
+1. Or run all the tests at once:
+
+        npm run all-test
+
+    or
+
+        yarn run all-test
+
+    With code coverage:
 
         npm run all-cover
 
+    or
+
+        yarn run all-cover
+
+### Run the tests for a single sample
+
+1. You must install dependencies at the root of the `nodejs-docs-samples`
+directory. You can do so with `yarn` or `npm`:
+
+        npm install
+
+    or
+
+        yarn install
+
+1. Change directory to one of the sample folders, e.g. `bigquery`:
+
+        cd bigquery/
+
+1. Run the tests (check the `package.json` file):
+
+        npm test
+
+    or
+
+        yarn test
+
+    or
+
+        npm run system-test
+
+    or
+
+        yarn run system-test
+
 ## Client libraries
 
 ### <img src="https://avatars2.githubusercontent.com/u/2810941?v=3&s=36" alt="Google Cloud Platform logo" title="Google Cloud Platform" align="left" height="36" width="36" style="margin-top: 9px;"/>Google Cloud Node.js client library
@@ -190,7 +262,9 @@ The recommended, idiomatic client for Google Cloud Platform services.
 
 ### <img src="https://avatars0.githubusercontent.com/u/1342004?v=3&s=36" alt="Google logo" title="Google" align="left" height="36" width="36" style="margin-top: 9px;"/>Google API Node.js client library
 
-An older Node.js client library for making REST requests to Google APIs.
+An older Node.js client library for making REST requests to Google APIs. Use
+this for Google Cloud APIs that are not yet supported by the Google Cloud
+Node.js client library.
 
 * [Documentation](http://google.github.io/google-api-nodejs-client/)
 * [Source code](https://github.com/google/google-api-nodejs-client)