builder.add(invokable);
      }
    }
    return new FactoryMethodReturnValueTester(cls, builder.build(), "public static methods");
  }

  /** Runs sanity tests against return values of static factory methods declared by a class. */
  public final class FactoryMethodReturnValueTester {
    private final Set<String> packagesToTest = new HashSet<>();
    private final Class<?> declaringClass;

    byte[] dest = new byte[3];
    HASH_ABCD.writeBytesTo(dest, 0, 2);
    assertThat(dest).isEqualTo(new byte[] {(byte) 0xaa, (byte) 0xbb, (byte) 0x00});
  }

  private static ClassSanityTester.FactoryMethodReturnValueTester sanityTester() {
    return new ClassSanityTester()
        .setDefault(byte[].class, new byte[] {1, 2, 3, 4})
        .setDistinctValues(byte[].class, new byte[] {1, 2, 3, 4}, new byte[] {5, 6, 7, 8})

    byte[] dest = new byte[3];
    HASH_ABCD.writeBytesTo(dest, 0, 2);
    assertThat(dest).isEqualTo(new byte[] {(byte) 0xaa, (byte) 0xbb, (byte) 0x00});
  }

  private static ClassSanityTester.FactoryMethodReturnValueTester sanityTester() {
    return new ClassSanityTester()
        .setDefault(byte[].class, new byte[] {1, 2, 3, 4})
        .setDistinctValues(byte[].class, new byte[] {1, 2, 3, 4}, new byte[] {5, 6, 7, 8})