Setup unit test for infinite loop detection

Needed a larger number of lines for issue to trigger. Used
grocery-shopping exercise as benchmark

Author: woojiahao

test/test_difflib_parser.py

@@ -1,29 +1,52 @@
-from difflib_parser import difflib_parser
+from difflib_parser import difflib_parser, DiffCode
 
 
 def test_diff_parser_same_lines():
     parser = difflib_parser.DifflibParser(["Hello world"], ["Hello world"])
     for diff in parser.iter_diffs():
-        assert diff.code == difflib_parser.DiffCode.SAME
+        assert diff.code == DiffCode.SAME
 
 
 def test_diff_parser_added_line():
     parser = difflib_parser.DifflibParser([], ["Hello world"])
     for diff in parser.iter_diffs():
-        assert diff.code == difflib_parser.DiffCode.RIGHT_ONLY
+        assert diff.code == DiffCode.RIGHT_ONLY
 
 
 def test_diff_parser_removed_line():
     parser = difflib_parser.DifflibParser(["Hello world"], [])
     for diff in parser.iter_diffs():
-        assert diff.code == difflib_parser.DiffCode.LEFT_ONLY
+        assert diff.code == DiffCode.LEFT_ONLY
+
+
+def test_diff_parser_edited_multi_line():
+    parser = difflib_parser.DifflibParser(
+        ["- Milk", "- Eggs", "Bread", "- Apples", "- Ham"],
+        ["- Milk", "- Eggs", "Bread", "- Apples", "- Ham1"],
+    )
+    expected_codes = [
+        DiffCode.SAME,
+        DiffCode.SAME,
+        DiffCode.SAME,
+        DiffCode.SAME,
+        DiffCode.CHANGED,
+    ]
+    i = 0
+    for diff in parser.iter_diffs():
+        assert diff.code == expected_codes[i]
+        if diff.code == DiffCode.CHANGED:
+            assert diff.line == "- Ham"
+            assert diff.newline == "- Ham1"
+            assert diff.left_changes == []
+            assert diff.right_changes == [5]
+        i += 1
 
 
 def test_diff_parser_changed_line_pattern_a():
     # Pattern a essentially looks at the case where existing characters were added/removed
     parser = difflib_parser.DifflibParser(["Hello world"], ["Hola world"])
     for diff in parser.iter_diffs():
-        assert diff.code == difflib_parser.DiffCode.CHANGED
+        assert diff.code == DiffCode.CHANGED
         assert diff.line == "Hello world"
         assert diff.newline == "Hola world"
         assert diff.left_changes == [1, 3, 4]
@@ -34,7 +57,7 @@ def test_diff_parser_changed_line_pattern_b():
     # Pattern b essentially looks at the case where only additions were included
     parser = difflib_parser.DifflibParser(["Hello world"], ["Hello world!"])
     for diff in parser.iter_diffs():
-        assert diff.code == difflib_parser.DiffCode.CHANGED
+        assert diff.code == DiffCode.CHANGED
         assert diff.line == "Hello world"
         assert diff.newline == "Hello world!"
         assert diff.left_changes == []
@@ -45,7 +68,7 @@ def test_diff_parser_changed_line_pattern_c():
     # Pattern c essentially looks at the case where only removals were included
     parser = difflib_parser.DifflibParser(["Hello world"], ["Hello worl"])
     for diff in parser.iter_diffs():
-        assert diff.code == difflib_parser.DiffCode.CHANGED
+        assert diff.code == DiffCode.CHANGED
         assert diff.line == "Hello world"
         assert diff.newline == "Hello worl"
         assert diff.left_changes == [10]