There are three kinds of compatibility we’re tracking:

 * **Binary compatibility** is the ability to compile a program against OkHttp 3.x, and then to run
   it against OkHttp 4.x. We’re using the excellent [japicmp][japicmp] library via its
   [Gradle plugin][japicmp_gradle] to enforce binary compatibility.

 * **Java source compatibility** is the ability to upgrade Java uses of OkHttp 3.x to 4.x without
   changing `.java` files.

            String nonceHex = bytesToHex(nonce);
            nonceSet.add(nonceHex);
        }

        // Verify that secure nonces provide excellent diversity
        // With 100 nonces and 16 random bytes, we should have all unique nonces
        assertEquals(100, nonceSet.size(), "Secure nonces should all be unique");
    }

    @Test