Add tests for verify_overlaps script

Refactor verify_overlaps to make it testable and add tests for the
comparison. It does make one significant change in behavior which is to
read each of the files produced by a bootclasspath_fragment into a dict
before comparison, rather than reading and comparing them a row at a
time. That allows it to reuse the code to read a CSV into a dict.

Bug: 194063708
Test: atest --host verify_overlaps_test
      m out/soong/hiddenapi/hiddenapi-flags.csv
      - manually change files to cause difference in flags to check
        that it detects the differences.
Change-Id: Ib70ac87fe089fc25e3bef18f367d4939bfc0cb8d
diff --git a/scripts/hiddenapi/verify_overlaps_test.py b/scripts/hiddenapi/verify_overlaps_test.py
new file mode 100755
index 0000000..1248890
--- /dev/null
+++ b/scripts/hiddenapi/verify_overlaps_test.py
@@ -0,0 +1,137 @@
+#!/usr/bin/env python
+#
+# Copyright (C) 2021 The Android Open Source Project
+#
+# 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.
+
+"""Unit tests for verify_overlaps_test.py."""
+import io
+import unittest
+
+from verify_overlaps import *
+
+class TestDetectOverlaps(unittest.TestCase):
+
+    def read_signature_csv_from_string_as_dict(self, csv):
+        with io.StringIO(csv) as f:
+            return read_signature_csv_from_stream_as_dict(f)
+
+    def test_match(self):
+        monolithic = self.read_signature_csv_from_string_as_dict('''
+Ljava/lang/Object;->hashCode()I,public-api,system-api,test-api
+Ljava/lang/Object;->toString()Ljava/lang/String;,blocked
+''')
+        modular = self.read_signature_csv_from_string_as_dict('''
+Ljava/lang/Object;->hashCode()I,public-api,system-api,test-api
+''')
+        mismatches = compare_signature_flags(monolithic, modular)
+        expected = []
+        self.assertEqual(expected, mismatches)
+
+    def test_mismatch_overlapping_flags(self):
+        monolithic = self.read_signature_csv_from_string_as_dict('''
+Ljava/lang/Object;->toString()Ljava/lang/String;,public-api
+''')
+        modular = self.read_signature_csv_from_string_as_dict('''
+Ljava/lang/Object;->toString()Ljava/lang/String;,public-api,system-api,test-api
+''')
+        mismatches = compare_signature_flags(monolithic, modular)
+        expected = [
+            (
+                'Ljava/lang/Object;->toString()Ljava/lang/String;',
+                ['public-api', 'system-api', 'test-api'],
+                ['public-api'],
+            ),
+        ]
+        self.assertEqual(expected, mismatches)
+
+
+    def test_mismatch_monolithic_blocked(self):
+        monolithic = self.read_signature_csv_from_string_as_dict('''
+Ljava/lang/Object;->hashCode()I,public-api,system-api,test-api
+Ljava/lang/Object;->toString()Ljava/lang/String;,blocked
+''')
+        modular = self.read_signature_csv_from_string_as_dict('''
+Ljava/lang/Object;->toString()Ljava/lang/String;,public-api,system-api,test-api
+''')
+        mismatches = compare_signature_flags(monolithic, modular)
+        expected = [
+            (
+                'Ljava/lang/Object;->toString()Ljava/lang/String;',
+                ['public-api', 'system-api', 'test-api'],
+                ['blocked'],
+            ),
+        ]
+        self.assertEqual(expected, mismatches)
+
+    def test_mismatch_modular_blocked(self):
+        monolithic = self.read_signature_csv_from_string_as_dict('''
+Ljava/lang/Object;->hashCode()I,public-api,system-api,test-api
+Ljava/lang/Object;->toString()Ljava/lang/String;,public-api,system-api,test-api
+''')
+        modular = self.read_signature_csv_from_string_as_dict('''
+Ljava/lang/Object;->toString()Ljava/lang/String;,blocked
+''')
+        mismatches = compare_signature_flags(monolithic, modular)
+        expected = [
+            (
+                'Ljava/lang/Object;->toString()Ljava/lang/String;',
+                ['blocked'],
+                ['public-api', 'system-api', 'test-api'],
+            ),
+        ]
+        self.assertEqual(expected, mismatches)
+
+    def test_missing_from_monolithic(self):
+        monolithic = self.read_signature_csv_from_string_as_dict('''
+Ljava/lang/Object;->hashCode()I,public-api,system-api,test-api
+''')
+        modular = self.read_signature_csv_from_string_as_dict('''
+Ljava/lang/Object;->toString()Ljava/lang/String;,public-api,system-api,test-api
+''')
+        mismatches = compare_signature_flags(monolithic, modular)
+        expected = [
+            (
+                'Ljava/lang/Object;->toString()Ljava/lang/String;',
+                ['public-api', 'system-api', 'test-api'],
+                [],
+            ),
+        ]
+        self.assertEqual(expected, mismatches)
+
+    def test_missing_from_modular(self):
+        # The modular dict defines the set of signatures to compare so an entry
+        # in the monolithic dict that does not have a corresponding entry in the
+        # modular dict is ignored.
+        monolithic = self.read_signature_csv_from_string_as_dict('''
+Ljava/lang/Object;->hashCode()I,public-api,system-api,test-api
+''')
+        modular = {}
+        mismatches = compare_signature_flags(monolithic, modular)
+        expected = []
+        self.assertEqual(expected, mismatches)
+
+    def test_blocked_missing_from_modular(self):
+        # The modular dict defines the set of signatures to compare so an entry
+        # in the monolithic dict that does not have a corresponding entry in the
+        # modular dict is ignored.
+        monolithic = self.read_signature_csv_from_string_as_dict('''
+Ljava/lang/Object;->hashCode()I,blocked
+''')
+        modular = {}
+        mismatches = compare_signature_flags(monolithic, modular)
+        expected = []
+        self.assertEqual(expected, mismatches)
+
+if __name__ == '__main__':
+    unittest.main(verbosity=2)