@Test
  public void testSeal_missingRequiredParameters_throwNullException() throws Exception {
    HpkeContextSender ctxSender = HpkeContextSender.getInstance(DEFAULT_SUITE_NAME);
    ctxSender.init(DEFAULT_PK, DEFAULT_INFO);
    assertThrows(NullPointerException.class,
        () -> ctxSender.seal(/* plaintext= */ null, DEFAULT_AAD));
  }
Tests for DuckTypedHpkeSpiTest. Essentially the same as the tests for HpkeContext but
with a "foreign" HPKE Provider inserted ahead of Conscrypt. That is, one which returns
SPI instances with all the correct methods but which don't inherit directly from "our"
HpkeSpi.
common/src/test/java/org/conscrypt/DuckTypedHpkeSpiTest.java