### Question:
B2ContentSourceWithByteProgressListener implements B2ContentSource { @Override public String toString() { return "B2ContentSourceWithByteProgressListener{" + source + "}"; } B2ContentSourceWithByteProgressListener(B2ContentSource source,
                                            B2ByteProgressListener listener); @Override long getContentLength(); @Override String getSha1OrNull(); @Override Long getSrcLastModifiedMillisOrNull(); @Override InputStream createInputStream(); @Override String toString();  }### Answer:
@Test public void testToString() throws Exception { assertTrue(source.toString().startsWith("B2ContentSourceWithByteProgressListener{Mock for B2ContentSource")); }