In the SIKE known answer tests, why is there only one secret key? I'm looking at the SIKE known answer tests and am realizing that I'm confused on all the different terms in a Diffie-Hellman key exchange. 

From the Wikipedia page, I would think there would be a public key and 2 secret keys, then a shared secret. However, the KAT provides a public key, a secret key, a shared secret, and a ciphertext. What exactly is the ciphertext, and where is the secret key?
This Wiki page describes SIDH, a key exchange protocol.

SIKE is a key encapsulation mechanism, like all entries in the NIST PQ competition, it has a different API.