public void testEmpty_transferFrom_positionGreaterThanSize_countGreaterThanSrcSize()
        throws IOException {
      long transferred = file.transferFrom(new ByteBufferChannel(buffer("111111")), 4, 12);
      assertEquals(0, transferred);
      assertContentEquals(bytes(), file);
    }
Actual test cases for testing RegularFiles.
jimfs/src/test/java/com/google/common/jimfs/RegularFileTest.java