title: Schema Registery Issue with Kafka Streams TopologyTestDriver with Avro record
body: <p>I am trying to test the kafka streams using the TopologyTestDriver. 
  I am sharing the code snippet and the error I am facing.</p>
  
  <pre><code>public class ToplogyTest extends AvroSourceJsonTopologyTestSupport {
      private static final String MOCK_SCHEMA_REGISTRY_URL = "mock://test:8081";
      private TopologyTestDriver testDriver;
      private TestInputTopic&lt;String, GenericRecord&gt; inputTopic;
      private MockSchemaRegistryClient schemaRegistryClient;
  }
  
    private final Properties props;
  
  public ToplogyTest () {
      super();
       props = new Properties();
      props.put(StreamsConfig.APPLICATION_ID_CONFIG, "streamsTest");
      props.put(StreamsConfig.BOOTSTRAP_SERVERS_CONFIG, "dummy:1234");
      props.put(StreamsConfig.DEFAULT_KEY_SERDE_CLASS_CONFIG, Serdes.String().getClass().getName());
      props.put(StreamsConfig.DEFAULT_VALUE_SERDE_CLASS_CONFIG, GenericAvroSerde.class);
      props.put(KafkaAvroSerializerConfig.SCHEMA_REGISTRY_URL_CONFIG, MOCK_SCHEMA_REGISTRY_URL); 
      schemaRegistryClient = new MockSchemaRegistryClient();
  }
  
   @BeforeEach
     public void setup() throws Exception {
  // Created the topology
   // Create test driver
          testDriver = new TopologyTestDriver(topology, props);
          // Create Serdes used for test record keys and values
          Serde&lt;String&gt; stringSerde = Serdes.String();
          Serde&lt;GenericRecord&gt; avroSerde = new GenericAvroSerde();
  final Map&lt;String,String&gt; avroSerdeConfig = new HashMap&lt;&gt;();
          avroSerdeConfig.put(KafkaAvroSerializerConfig.SCHEMA_REGISTRY_URL_CONFIG, MOCK_SCHEMA_REGISTRY_URL);
          avroSerde.configure(avroSerdeConfig, false);
          usersTopic = testDriver.createInputTopic(
                  "input-topic",
                  stringSerde.serializer(),
                  avroSerde.serializer());
  }
    @Test
    public void Test(){
   usersTopic.pipeInput("null",record);
  }
  </code></pre>
  
  <blockquote>
    <p>Error org.apache.kafka.common.errors.SerializationException: Error
    serializing Avro message  Suppressed:
    java.lang.IllegalArgumentException: Please always:   Initialize the
    test driver at the end of setup before each test using provided
    method;   Close the test driver after each test using provided method.
    Caused by: java.net.MalformedURLException: unknown protocol: mock at
    java.net.URL.(URL.java:618) at java.net.URL.(URL.java:508)
    at java.net.URL.(URL.java:457) at
    io.confluent.kafka.schemaregistry.client.rest.RestService.sendHttpRequest(RestService.java:
    152)</p>
  </blockquote>
  
  <p>What i understood here is I am not able to register the mock schema registry. Is there anyone faced similar issue ? </p>