Add test for ollamaChat.generate for the case when ollamaChat is called with the system prompt defined

Author: vpapanasta

tests/tollamaChat.m

@@ -39,6 +39,13 @@ function doGenerate(testCase,StringInputs)
             testCase.verifyGreaterThan(strlength(response),0);
         end
 
+        function doGenerateUsingSystemPrompt(testCase)
+            chat = ollamaChat("mistral","You are a helpful assistant");
+            response = testCase.verifyWarningFree(@() generate(chat,"Hi"));
+            testCase.verifyClass(response,'string');
+            testCase.verifyGreaterThan(strlength(response),0);
+        end
+
         function extremeTopK(testCase)
             % setting top-k to k=1 leaves no random choice,
             % so we expect to get a fixed response.