refactor: address code review feedback

Makefile.am:
- Replace 4 hardcoded parallel commands with loop over FUNC_TEST_GROUPS
- Easy to extend by adding group numbers to the variable

functionaltests.c:
- Remove test counts from comments (prone to becoming outdated)
- Restore previous comment style with === separators for readability
- Replace switch with groups[] array structure for extensibility

proftest.h:
- Fix comment to describe current state, not the change made

CONTRIBUTING.md:
- Document test groups and parallel execution commands
- Add instructions for adding new test groups

Makefile.am

@@ -308,18 +308,22 @@ tests_functionaltests_functionaltests_LDADD = -lcmocka -lstabber @FORKPTY_LIB@
 
 # Parallel functional tests target (~3x faster than sequential)
 # Usage: make check-functional-parallel
+# To add more groups: increase FUNC_TEST_GROUPS and add group in functionaltests.c
+FUNC_TEST_GROUPS = 1 2 3 4
+
 check-functional-parallel: tests/functionaltests/functionaltests
-	@echo "Running functional tests in parallel (4 groups)..."
+	@echo "Running functional tests in parallel ($(words $(FUNC_TEST_GROUPS)) groups)..."
 	@mkdir -p $(builddir)/test-logs
-	@failed=0; \
-	./tests/functionaltests/functionaltests 1 > $(builddir)/test-logs/group1.log 2>&1 & pid1=$$!; \
-	./tests/functionaltests/functionaltests 2 > $(builddir)/test-logs/group2.log 2>&1 & pid2=$$!; \
-	./tests/functionaltests/functionaltests 3 > $(builddir)/test-logs/group3.log 2>&1 & pid3=$$!; \
-	./tests/functionaltests/functionaltests 4 > $(builddir)/test-logs/group4.log 2>&1 & pid4=$$!; \
-	wait $$pid1 || { echo "Group 1 FAILED (exit $$?)"; cat $(builddir)/test-logs/group1.log; failed=1; }; \
-	wait $$pid2 || { echo "Group 2 FAILED (exit $$?)"; cat $(builddir)/test-logs/group2.log; failed=1; }; \
-	wait $$pid3 || { echo "Group 3 FAILED (exit $$?)"; cat $(builddir)/test-logs/group3.log; failed=1; }; \
-	wait $$pid4 || { echo "Group 4 FAILED (exit $$?)"; cat $(builddir)/test-logs/group4.log; failed=1; }; \
+	@pids=""; \
+	for g in $(FUNC_TEST_GROUPS); do \
+		./tests/functionaltests/functionaltests $$g > $(builddir)/test-logs/group$$g.log 2>&1 & \
+		pids="$$pids $$!"; \
+	done; \
+	failed=0; i=1; \
+	for pid in $$pids; do \
+		wait $$pid || { echo "Group $$i FAILED"; cat $(builddir)/test-logs/group$$i.log; failed=1; }; \
+		i=$$((i + 1)); \
+	done; \
 	echo "=== Test Results Summary ==="; \
 	grep -E 'PASSED|FAILED|Running' $(builddir)/test-logs/group*.log || true; \
 	if [ $$failed -ne 0 ]; then echo "FUNCTIONAL TESTS FAILED"; exit 1; fi; \