Don't expose extract and expand on this class yet because we don't know how best to expose verify functionality, continue testing the stages using the private methods.
diff --git a/tests/hazmat/primitives/utils.py b/tests/hazmat/primitives/utils.py
index 2584272..5a8dc3a 100644
--- a/tests/hazmat/primitives/utils.py
+++ b/tests/hazmat/primitives/utils.py
@@ -326,7 +326,7 @@
         backend=backend
     )
 
-    prk = hkdf.extract(binascii.unhexlify(params["ikm"]))
+    prk = hkdf._extract(binascii.unhexlify(params["ikm"]))
 
     assert prk == binascii.unhexlify(params["prk"])
 
@@ -340,7 +340,7 @@
         backend=backend
     )
 
-    okm = hkdf.expand(binascii.unhexlify(params["prk"]))
+    okm = hkdf._expand(binascii.unhexlify(params["prk"]))
 
     assert okm == binascii.unhexlify(params["okm"])