Extended memory for adding language support

.serena/memories/adding_new_language_support_guide.md

@@ -186,9 +186,22 @@ class Program {
 
 ## Step 4: Test Suite
 
+Testing the language server implementation is of crucial importance, and the tests will
+form the main part of the review process. Make sure that the tests are up to the standard
+of Serena to make the review go smoother.
+
+General rules for tests:
+
+1. Tests for symbols and references should always check that the expected symbol names and references were actually found.
+   Just testing that a list came back or that the result is not None is insufficient.
+2. Tests should never be skipped, the only exception is skipping based on some package being available or on an unsupported OS.
+3. Tests should run in CI, check if there is a suitable GitHub action for installing the dependencies.
+
 ### 4.1 Basic Tests
 
-Create `test/solidlsp/new_language/test_new_language_basic.py`. You should at least test:
+Create `test/solidlsp/new_language/test_new_language_basic.py`.
+Have a look at the structure of existing tests, for example, in `test/solidlsp/php/test_php_basic.py`
+You should at least test:
 
 1. Finding symbols
 2. Finding within-file references