@Test
  public void testExport_lowerEdgeLength() throws Exception {
    final HpkeContextSender ctxSender = createDefaultHpkeContextSender();
    final byte[] enc = ctxSender.getEncapsulated();
    final byte[] export = ctxSender.export(/* length= */ 0, DEFAULT_EXPORTER_CONTEXT);
    assertNotNull(enc);
    assertNotNull(export);
    assertThrows(IllegalArgumentException.class,
        () -> ctxSender.export(/* length= */ -1, DEFAULT_EXPORTER_CONTEXT));
  }
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