adapt protocol buffers module to JUnit 4

Author: diegomarquezp

google-http-client-protobuf/src/main/java/com/google/api/client/protobuf/ProtocolBuffers.java

@@ -37,10 +37,15 @@
 public class ProtocolBuffers {
 
   /** {@code "application/x-protobuf"} content type. */
-  public static final String CONTENT_TYPE = "application/x-protobuf";
+  public static final String CONTENT_TYPE;
 
   /** {@code "application/x-protobuffer"} content type. */
-  public static final String ALT_CONTENT_TYPE = "application/x-protobuffer";
+  public static final String ALT_CONTENT_TYPE;
+
+  static {
+    CONTENT_TYPE = "application/x-protobuf";
+    ALT_CONTENT_TYPE = "application/x-protobuffer";
+  }
 
   /**
    * Parses protocol buffer content from an input stream (closing the input stream) into a protocol

google-http-client-protobuf/src/test/java/com/google/api/client/protobuf/ProtocolBuffersTest.java

@@ -14,16 +14,22 @@
 
 package com.google.api.client.protobuf;
 
+import static org.junit.Assert.assertEquals;
+
 import java.io.ByteArrayInputStream;
-import junit.framework.TestCase;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
 
 /**
  * Tests {@link ProtocolBuffers}.
  *
  * @author Yaniv Inbar
  */
-public class ProtocolBuffersTest extends TestCase {
+@RunWith(JUnit4.class)
+public class ProtocolBuffersTest {
 
+  @Test
   public void testParseAndClose() throws Exception {
     SimpleProto.TestMessage mockResponse =
         SimpleProto.TestMessage.newBuilder()