@Test
  public void testRegisterKeyManager_deprecated_keyManagerIsNull_shouldThrowException()
      throws Exception {
    IllegalArgumentException e =
        assertThrows(
            IllegalArgumentException.class,
            () -> Registry.registerKeyManager(AeadConfig.AES_CTR_HMAC_AEAD_TYPE_URL, null));
    assertThat(e.toString()).contains("must be non-null");
  }
Returns the type URL that identifies the key type of keys managed by this KeyManager.
java_src/src/test/java/com/google/crypto/tink/RegistryTest.java