### Question:
B2ContentSourceWithByteProgressListener implements B2ContentSource { @Override public String getSha1OrNull() throws IOException { return source.getSha1OrNull(); } B2ContentSourceWithByteProgressListener(B2ContentSource source,
                                            B2ByteProgressListener listener); @Override long getContentLength(); @Override String getSha1OrNull(); @Override Long getSrcLastModifiedMillisOrNull(); @Override InputStream createInputStream(); @Override String toString();  }### Answer:
@Test public void testGetSha1OrNull() throws Exception { when(wrappedSource.getSha1OrNull()).thenReturn("sha1"); assertEquals("sha1", source.getSha1OrNull()); }