public void testNonEmpty_read_partial_fromEnd_singleBuffer() throws IOException {
      fillContent("2222222222");
      ByteBuffer buffer = ByteBuffer.allocate(3);
      assertEquals(2, file.read(8, buffer));
      assertBufferEquals("220", 1, buffer);
    }
Actual test cases for testing RegularFiles.
jimfs/src/test/java/com/google/common/jimfs/RegularFileTest.java