package com.atlassian.gzipfilter;
   
   import junit.framework.TestCase;
   
   import javax.servlet.ServletOutputStream;
   import javax.servlet.http.HttpServletResponse;
   import java.io.ByteArrayInputStream;
   import java.io.ByteArrayOutputStream;
   import java.io.IOException;
  import java.util.zip.GZIPInputStream;
  
  import static org.hamcrest.MatcherAssert.assertThat;
  import static org.hamcrest.core.IsEqual.equalTo;
  import static org.mockito.Mockito.mock;
  import static org.mockito.Mockito.when;
  
  public class TestGzipResponseWrapper extends TestCase
  {
      public void testCreateValidGzipStreamEvenWhenNothingWrittenToResponse() throws Exception
      {
          final HttpServletResponse mockHttpResponse = mock(HttpServletResponse.class);
          final ByteArrayServletOutputStream byteOutputStream = new ByteArrayServletOutputStream();
          when(mockHttpResponse.getOutputStream())
                  .thenReturn(byteOutputStream);
  
          final GzipResponseWrapper gzipResponseWrapper = new GzipResponseWrapper(mockHttpResponse, "UTF-8");
  
          gzipResponseWrapper.finishResponse();
  
          //verify an empty but valid gzip stream was constructed
          final byte[] content = byteOutputStream.getContent();
          final GZIPInputStream gzipInputStream = new GZIPInputStream(new ByteArrayInputStream(content));
          assertThat(gzipInputStream.read(), equalTo(-1));
      }
  
      static class ByteArrayServletOutputStream extends ServletOutputStream
      {
          private final ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
  
          @Override
          public void write(final int b) throws IOException
          {
              outputStream.write(b);
          }
  
          byte[] getContent()
          {
              return outputStream.toByteArray();
          }
      }
  }