Add tests for bump_changelog

Author: Pierre-Sassoulas

script/test_bump_changelog.py

@@ -1,9 +1,83 @@
 import pytest
-from bump_changelog import get_next_version
+from bump_changelog import get_next_version, transform_content
 
 
 @pytest.mark.parametrize(
     "version,expected", [["2.6.1", "2.6.2"], ["2.6.1-dev0", "2.6.2-dev0"]]
 )
 def test_get_next_version(version, expected):
     assert get_next_version(version) == expected
+
+
+@pytest.mark.parametrize(
+    "old_content,expected_error",
+    [
+        [
+            """
+What's New in astroid 2.6.1?
+============================
+Release Date: TBA
+
+What's New in astroid 2.6.0?
+============================
+Release Date: TBA
+""",
+            "More than one release date 'TBA'",
+        ],
+        [
+            """===================
+astroid's ChangeLog
+===================
+
+What's New in astroid 2.6.0?
+============================
+Release Date: TBA
+""",
+            "text for this version '2.6.1' did not exists",
+        ],
+        [
+            """
+What's New in astroid 2.6.2?
+============================
+Release Date: TBA
+
+What's New in astroid 2.6.1?
+============================
+Release Date: 2012-02-05
+""",
+            "the next version '2.6.2' already exists",
+        ],
+    ],
+)
+def test_update_content_error(old_content, expected_error):
+    with pytest.raises(AssertionError, match=expected_error):
+        transform_content(old_content, "2.6.1", "2.6.2")
+
+
+def test_update_content():
+    old_content = """
+===================
+astroid's ChangeLog
+===================
+
+What's New in astroid 2.6.1?
+============================
+Release Date: TBA
+"""
+    expected_beginning = """
+===================
+astroid's ChangeLog
+===================
+
+What's New in astroid 2.6.2?
+============================
+Release Date: TBA
+
+
+
+What's New in astroid 2.6.1?
+============================
+Release Date: 20"""
+
+    new_content = transform_content(old_content, "2.6.1", "2.6.2")
+    assert new_content.startswith(expected_beginning)