Update Eclipse dev guide

Adds a short mention how to configure project to run tests directly from
Eclipse.

Release-Notes: skip
Change-Id: I7a2daf1a67accb3cab1e141b3e166b43ab6dd77c
diff --git a/Documentation/dev-eclipse.txt b/Documentation/dev-eclipse.txt
index dce5eb0..e0344a8 100644
--- a/Documentation/dev-eclipse.txt
+++ b/Documentation/dev-eclipse.txt
@@ -81,6 +81,10 @@
 link:dev-build-plugins.html#_bundle_custom_plugin_in_release_war[bundling in release.war]
 and run `tools/eclipse/project.py`.
 
+If a plugin requires additional test dependencies (not available in the Gerrit), then in order to
+execute tests directly from Eclipse, that plugin must be also added to `CUSTOM_PLUGINS_TEST_DEPS`
+list in `tools/bzl/plugins.bzl` (note that `tools/eclipse/project.py` has to be run again).
+
 == Java Versions
 
 Java 11 is supported as a default, but some adjustments must be done for other JDKs: