tests: all 16 tests now sourced from org (doctor→diagnostics rename, orphaned tests adopted)

org/system-model-provider.org

@@ -161,3 +161,23 @@ If API-KEY is nil, reads from environment."
   :priority 50
   :trigger (lambda (ctx) (declare (ignore ctx)) nil))
 #+end_src
+
+* Test Suite
+#+begin_src lisp :tangle ../tests/llm-gateway-tests.lisp
+(eval-when (:compile-toplevel :load-toplevel :execute)
+  (ql:quickload :fiveam :silent t))
+
+(defpackage :passepartout-llm-gateway-tests
+  (:use :cl :passepartout)
+  (:export #:llm-gateway-suite))
+
+(in-package :passepartout-llm-gateway-tests)
+
+(fiveam:def-suite llm-gateway-suite :description "Tests for the LLM provider backend")
+(fiveam:in-suite llm-gateway-suite)
+
+(fiveam:test test-provider-rejects-bad-keyword
+  "Verify that provider-openai-request returns :error for an unregistered provider."
+  (let ((result (provider-openai-request "hello" "test" :provider :not-a-real-provider)))
+    (fiveam:is (eq (getf result :status) :error))))
+#+end_src