Fix unit tests

Author: dan-rubinstein

x-pack/plugin/inference/src/test/java/org/elasticsearch/xpack/inference/services/elastic/ElasticInferenceServiceTests.java

@@ -319,6 +319,19 @@ public void testCheckModelConfig_ReturnsNewModelReference() throws IOException {
         var senderFactory = HttpRequestSenderTests.createSenderFactory(threadPool, clientManager);
 
         try (var service = createService(senderFactory, getUrl(webServer))) {
+            String responseJson = """
+                {
+                    "data": [
+                        {
+                            "hello": 2.1259406,
+                            "greet": 1.7073475
+                        }
+                    ]
+                }
+                """;
+
+            webServer.enqueue(new MockResponse().setResponseCode(200).setBody(responseJson));
+
             var model = ElasticInferenceServiceSparseEmbeddingsModelTests.createModel(getUrl(webServer), "my-model-id");
             PlainActionFuture<Model> listener = new PlainActionFuture<>();
             service.checkModelConfig(model, listener);