public void testNonEmpty_write_partial_fromPastEnd_multipleBuffers() throws IOException {
      fillContent("222222");
      assertEquals(4, file.write(10, buffers("11", "33")));
      assertContentEquals("22222200001133", file);
    }
Actual test cases for testing RegularFiles.
jimfs/src/test/java/com/google/common/jimfs/RegularFileTest.java