public void testNonEmpty_read_partial_fromMiddle_byteArray() throws IOException {
      fillContent("22223333");
      byte[] array = new byte[3];
      assertEquals(3, file.read(3, array, 0, array.length));
      assertArrayEquals(bytes("233"), array);
      array = new byte[10];
      assertEquals(3, file.read(3, array, 1, 3));
      assertArrayEquals(bytes("0233000000"), array);
    }
Actual test cases for testing RegularFiles.
jimfs/src/test/java/com/google/common/jimfs/RegularFileTest.java