Documentation: Add missing plugin standalone and in-tree testing

Bug: Issue 12096
Change-Id: I0b33f30d9bc54dbf0d0c33803831151f666314a5

src/main/resources/Documentation/build.md

diff --git a/src/main/resources/Documentation/build.md b/src/main/resources/Documentation/build.md
index 213ebe6..e9e055e 100644
--- a/src/main/resources/Documentation/build.md
+++ b/src/main/resources/Documentation/build.md
@@ -35,6 +35,12 @@
   bazel-bin/lib@PLUGIN@__plugin-src.jar
 ```
 
+To execute the tests run:
+
+```
+  bazel test //...
+```
+
 This project can be imported into the Eclipse IDE:
 
 ```
@@ -73,6 +79,12 @@
   ./tools/eclipse/project.py
 ```
 
+To execute the tests run:
+
+```
+  bazel test plugins/@PLUGIN@:@PLUGIN@_tests
+```
+
 How to build the Gerrit Plugin API is described in the [Gerrit
 documentation](../../../Documentation/dev-bazel.html#_extension_and_plugin_api_jar_files).