Refactor some certificate verification tests in preparation to adding

net/data/verify_certificate_chain_unittest/generate-intermediate-unknown-critical-extension.py

Index: net/data/verify_certificate_chain_unittest/generate-intermediate-unknown-critical-extension.py
diff --git a/net/data/verify_certificate_chain_unittest/generate-intermediate-unknown-critical-extension.py b/net/data/verify_certificate_chain_unittest/generate-intermediate-unknown-critical-extension.py
index b4bffa1a60eb172cbf36a224bc5c8f1dcf30bc4f..0f3cfe23e54c03490a805379742b237358661aa7 100755
--- a/net/data/verify_certificate_chain_unittest/generate-intermediate-unknown-critical-extension.py
+++ b/net/data/verify_certificate_chain_unittest/generate-intermediate-unknown-critical-extension.py
@@ -10,7 +10,7 @@ unrecognized critical extension."""
 
 import common
 
-# Self-signed root certificate (part of trust store).
+# Self-signed root certificate (used as trust anchor).
 root = common.create_self_signed_root_certificate('Root')
 
 # Intermediate that has an unknown critical extension.
@@ -21,9 +21,12 @@ intermediate.get_extensions().add_property('1.2.3.4',
 # Target certificate.
 target = common.create_end_entity_certificate('Target', intermediate)
 
-chain = [target, intermediate]
-trusted = [root]
-time = common.DEFAULT_TIME
-verify_result = False
+# Write the test chain to a file.
+test = common.TestData()
+test.description = __doc__
+test.chain = [target, intermediate]
+test.trust_anchor = common.TrustAnchor(root, constrained=False)
+test.utc_time = common.DEFAULT_TIME
+test.verify_result = False
 
-common.write_test_file(__doc__, chain, trusted, time, verify_result)
+test.write_to_file(common.get_default_pem_path())