test: cover config migration dry run

tests/config/test_config_source.py

@@ -1,71 +1,60 @@
 from __future__ import annotations
 
+from copy import deepcopy
+
+import pytest
+
+from cleo.io.buffered_io import BufferedIO
+
 from poetry.config.config_source import UNSET
 from poetry.config.config_source import ConfigSourceMigration
 from poetry.config.dict_config_source import DictConfigSource
 
 
-def test_config_source_migration_rename_key() -> None:
-    config_data = {
+@pytest.fixture
+def config_source() -> DictConfigSource:
+    config_source = DictConfigSource()
+    config_source._config = {
         "virtualenvs": {
             "prefer-active-python": True,
         },
         "system-git-client": True,
     }
 
-    config_source = DictConfigSource()
-    config_source._config = config_data
+    return config_source
+
 
+def test_config_source_migration_rename_key(config_source: DictConfigSource) -> None:
     migration = ConfigSourceMigration(
         old_key="virtualenvs.prefer-active-python",
         new_key="virtualenvs.use-poetry-python",
     )
 
     migration.apply(config_source)
 
-    assert config_source._config == {
+    assert config_source.config == {
         "virtualenvs": {
             "use-poetry-python": True,
         },
         "system-git-client": True,
     }
 
 
-def test_config_source_migration_remove_key() -> None:
-    config_data = {
-        "virtualenvs": {
-            "prefer-active-python": True,
-        },
-        "system-git-client": True,
-    }
-
-    config_source = DictConfigSource()
-    config_source._config = config_data
-
+def test_config_source_migration_remove_key(config_source: DictConfigSource) -> None:
     migration = ConfigSourceMigration(
         old_key="virtualenvs.prefer-active-python",
         new_key=None,
     )
 
     migration.apply(config_source)
 
-    assert config_source._config == {
+    assert config_source.config == {
         "virtualenvs": {},
         "system-git-client": True,
     }
 
 
-def test_config_source_migration_unset_value() -> None:
-    config_data = {
-        "virtualenvs": {
-            "prefer-active-python": True,
-        },
-        "system-git-client": True,
-    }
-
-    config_source = DictConfigSource()
-    config_source._config = config_data
-
+def test_config_source_migration_unset_value(config_source: DictConfigSource) -> None:
     migration = ConfigSourceMigration(
         old_key="virtualenvs.prefer-active-python",
         new_key="virtualenvs.use-poetry-python",
@@ -74,23 +63,15 @@ def test_config_source_migration_unset_value() -> None:
 
     migration.apply(config_source)
 
-    assert config_source._config == {
+    assert config_source.config == {
         "virtualenvs": {},
         "system-git-client": True,
     }
 
 
-def test_config_source_migration_complex_migration() -> None:
-    config_data = {
-        "virtualenvs": {
-            "prefer-active-python": True,
-        },
-        "system-git-client": True,
-    }
-
-    config_source = DictConfigSource()
-    config_source._config = config_data
-
+def test_config_source_migration_complex_migration(
+    config_source: DictConfigSource,
+) -> None:
     migration = ConfigSourceMigration(
         old_key="virtualenvs.prefer-active-python",
         new_key="virtualenvs.use-poetry-python",
@@ -99,9 +80,71 @@ def test_config_source_migration_complex_migration() -> None:
 
     migration.apply(config_source)
 
-    assert config_source._config == {
+    assert config_source.config == {
         "virtualenvs": {
             "use-poetry-python": None,
         },
         "system-git-client": True,
     }
+
+
+@pytest.mark.parametrize(
+    ("migration", "expected_result", "expected_output"),
+    [
+        pytest.param(
+            ConfigSourceMigration(
+                old_key="virtualenvs.prefer-active-python",
+                new_key="virtualenvs.use-poetry-python",
+            ),
+            True,
+            (
+                "virtualenvs.prefer-active-python = true -> "
+                "virtualenvs.use-poetry-python = true"
+            ),
+            id="rename-key",
+        ),
+        pytest.param(
+            ConfigSourceMigration(
+                old_key="virtualenvs.prefer-active-python",
+                new_key=None,
+            ),
+            True,
+            "virtualenvs.prefer-active-python = true -> Removed from config",
+            id="remove-key",
+        ),
+        pytest.param(
+            ConfigSourceMigration(
+                old_key="virtualenvs.prefer-active-python",
+                new_key="virtualenvs.use-poetry-python",
+                value_migration={True: UNSET, False: True},
+            ),
+            True,
+            (
+                "virtualenvs.prefer-active-python = true -> "
+                "virtualenvs.use-poetry-python = Not explicit set"
+            ),
+            id="unset-value",
+        ),
+        pytest.param(
+            ConfigSourceMigration(
+                old_key="virtualenvs.missing-key",
+                new_key="virtualenvs.use-poetry-python",
+            ),
+            False,
+            "",
+            id="missing-key",
+        ),
+    ],
+)
+def test_config_source_migration_dry_run(
+    config_source: DictConfigSource,
+    migration: ConfigSourceMigration,
+    expected_result: bool,
+    expected_output: str,
+) -> None:
+    original_config = deepcopy(config_source.config)
+    io = BufferedIO()
+
+    assert migration.dry_run(config_source, io) is expected_result
+    assert io.fetch_output().strip() == expected_output
+    assert config_source.config == original_config