@Theory
  public void testEncryptDecryptRandomAccess(
      @FromDataPoints("randomAccessTestVectors") AesGcmHkdfStreamingTestVector t) throws Exception {
    StreamingTestUtil.testEncryptDecryptRandomAccess(
        t.directConstructorAgs, t.directConstructorAgs.getFirstSegmentOffset(), t.plaintextSize);
  }
Encrypt and then decrypt partially, and check that the result is the same.
java_src/src/test/java/com/google/crypto/tink/subtle/AesGcmHkdfStreamingTest.java