Added unit tests for Worker Builder IKinesisProxy injection validation

Refactored unit tests as per comments in the pull request.

src/main/java/com/amazonaws/services/kinesis/clientlibrary/lib/worker/Worker.java

@@ -997,6 +997,11 @@ public class Worker implements Runnable {
                 metricsFactory, execService);
     }
 
+    @VisibleForTesting
+    StreamConfig getStreamConfig() {
+        return streamConfig;
+    }
+
     /**
      * Given configuration, returns appropriate metrics factory.
      * 

src/test/java/com/amazonaws/services/kinesis/clientlibrary/lib/worker/WorkerTest.java

@@ -90,6 +90,7 @@ import com.amazonaws.services.kinesis.clientlibrary.interfaces.v2.IRecordProcess
 import com.amazonaws.services.kinesis.clientlibrary.lib.worker.Worker.WorkerCWMetricsFactory;
 import com.amazonaws.services.kinesis.clientlibrary.lib.worker.Worker.WorkerThreadPoolExecutor;
 import com.amazonaws.services.kinesis.clientlibrary.proxies.IKinesisProxy;
+import com.amazonaws.services.kinesis.clientlibrary.proxies.KinesisProxy;
 import com.amazonaws.services.kinesis.clientlibrary.proxies.KinesisLocalFileProxy;
 import com.amazonaws.services.kinesis.clientlibrary.proxies.util.KinesisLocalFileDataCreator;
 import com.amazonaws.services.kinesis.clientlibrary.types.ExtendedSequenceNumber;
@@ -1474,6 +1475,31 @@ public class WorkerTest {
 
     }
 
+    @Test
+    public void testBuilderWithDefaultKinesisProxy() {
+        IRecordProcessorFactory recordProcessorFactory = mock(IRecordProcessorFactory.class);
+        Worker worker = new Worker.Builder()
+            .recordProcessorFactory(recordProcessorFactory)
+            .config(config)
+            .build();
+        Assert.assertNotNull(worker.getStreamConfig().getStreamProxy());
+        Assert.assertTrue(worker.getStreamConfig().getStreamProxy() instanceof KinesisProxy);
+    }
+
+    @Test
+    public void testBuilderWhenKinesisProxyIsSet() {
+        IRecordProcessorFactory recordProcessorFactory = mock(IRecordProcessorFactory.class);
+        // Create an instance of KinesisLocalFileProxy for injection and validation
+        IKinesisProxy kinesisProxy = mock(KinesisLocalFileProxy.class);
+        Worker worker = new Worker.Builder()
+            .recordProcessorFactory(recordProcessorFactory)
+            .config(config)
+            .kinesisProxy(kinesisProxy)
+            .build();
+        Assert.assertNotNull(worker.getStreamConfig().getStreamProxy());
+        Assert.assertTrue(worker.getStreamConfig().getStreamProxy() instanceof KinesisLocalFileProxy);
+    }
+
     private abstract class InjectableWorker extends Worker {
         InjectableWorker(String applicationName, IRecordProcessorFactory recordProcessorFactory,
                 KinesisClientLibConfiguration config, StreamConfig streamConfig,