private static TestPrimitiveA getPrimitiveAHmacKey(HmacKey key) {
    return new TestPrimitiveA();
  }
Tests that key parsing via the serialization registry works as expected.

<p>NOTE: This adds a parser to the MutableSerializationRegistry, which no other test uses.
java_src/src/test/java/com/google/crypto/tink/KeysetHandleTest.java