Add unit tests for LlamaErrorResponse to validate error handling from HTTP responses

Author: Jan-Kazlouski-elastic

x-pack/plugin/inference/src/test/java/org/elasticsearch/xpack/inference/services/llama/response/LlamaErrorResponseTests.java

@@ -0,0 +1,34 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License
+ * 2.0; you may not use this file except in compliance with the Elastic License
+ * 2.0.
+ */
+
+package org.elasticsearch.xpack.inference.services.llama.response;
+
+import org.apache.http.HttpResponse;
+import org.elasticsearch.test.ESTestCase;
+import org.elasticsearch.xpack.inference.external.http.HttpResult;
+
+import java.nio.charset.StandardCharsets;
+
+import static org.mockito.Mockito.mock;
+
+public class LlamaErrorResponseTests extends ESTestCase {
+
+    public static final String ERROR_RESPONSE_JSON = """
+        {
+            "error": "A valid user token is required"
+        }
+        """;
+
+    public void testFromResponse() {
+        var errorResponse = LlamaErrorResponse.fromResponse(
+            new HttpResult(mock(HttpResponse.class), ERROR_RESPONSE_JSON.getBytes(StandardCharsets.UTF_8))
+        );
+        assertNotNull(errorResponse);
+        assertEquals(ERROR_RESPONSE_JSON, errorResponse.getErrorMessage());
+    }
+
+}