@Test
  public void testAmbiguousDecoding() throws DecodingException {
    byte[] b16 = Base32String.decode("7777777777777777"); // 16 7s.
    byte[] b17 = Base32String.decode("77777777777777777"); // 17 7s.
    assertThat(b17).isEqualTo(b16);
  }
Base32String implementation is not the same as that of RFC 4648, it drops
the last incomplete chunk and thus accepts encoded strings that should have
been rejected; also this results in multiple encoded strings being decoded
to the same byte array.
This test will catch any changes made regarding this behavior.
javatests/com/google/android/apps/authenticator/util/Base32StringTest.java