test: invariant preservation test

Signed-off-by: William Woodruff <[email protected]>

test/unit/test_transparency.py

@@ -0,0 +1,33 @@
+# Copyright 2022 The Sigstore Authors
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from base64 import b64encode
+import pytest
+from sigstore.transparency import LogEntry
+
+
+class TestLogEntry:
+    def test_consistency(self):
+        with pytest.raises(
+            ValueError, match=r"Log entry must have either inclusion proof or promise"
+        ):
+            LogEntry(
+                uuid="fake",
+                body=b64encode("fake".encode()),
+                integrated_time=0,
+                log_id="1234",
+                log_index=1,
+                inclusion_proof=None,
+                inclusion_promise=None,
+            )