added more fine-grained mocking functionality

Author: arcuri82

core/src/main/kotlin/org/evomaster/core/llm/mock/LlmMockResponse.kt

@@ -3,9 +3,9 @@ package org.evomaster.core.llm.mock
 class LlmMockResponse(
 
     /**
-     * The response that will be returned by the LLM
+     * The response producer that will be returned by the LLM, given an input text from user
      */
-    val response: String,
+    val responseProducer: (String) -> String,
 
     /**
      * Lambda that, given as input a request from the client, decides whether this response should be returned

core/src/main/kotlin/org/evomaster/core/llm/mock/MockChatModel.kt

@@ -33,7 +33,16 @@ class MockChatModel : ChatModel {
          * decides whether this response should be returned
          */
         fun mockResponse(response: String, matcher: (String) -> Boolean){
-            responses.add(LlmMockResponse(response, matcher))
+            responses.add(LlmMockResponse({req -> response}, matcher))
+        }
+
+        /**
+         * Specify a producer of responses if the text of the query from user does match the matcher.
+         * Input for both lambdas is such text.
+         * This is useful when the response for same query might be different
+         */
+        fun mockResponse(responseProducer: (String) -> String, matcher: (String) -> Boolean){
+            responses.add(LlmMockResponse(responseProducer, matcher))
         }
     }
 
@@ -45,7 +54,7 @@ class MockChatModel : ChatModel {
 
         val text = chatRequest.messages().joinToString { it.toString() }
 
-        val res = responses.find { mock -> mock.matcher(text) }?.response
+        val res = responses.find { mock -> mock.matcher(text) }?.responseProducer(text)
             ?: "Hei! You forgot to setup the mock for me"
 
         return ChatResponse.builder().aiMessage(AiMessage.from(res)).build()

core/src/test/kotlin/org/evomaster/core/llm/LlmSupportMockTest.kt

@@ -27,4 +27,22 @@ class LlmSupportMockTest {
         assertEquals("YES", LlmSupport.chat(model, firstPrompt))
         assertEquals("NO", LlmSupport.chat(model, secondPrompt))
     }
+
+    @Test
+    fun testResponseProducer(){
+        val model = LlmSupport.createModel(LlmProvider.MOCK)
+
+        val prompt = "Give me a random value"
+        val x = arrayOf(0)
+
+        MockChatModel.reset()
+        MockChatModel.mockResponse({_ -> "${x[0]++}"}){it.contains("random")}
+
+        val n = 10
+        repeat(n){
+            LlmSupport.chat(model, prompt)
+        }
+
+        assertEquals(n, x[0])
+    }
 }