Make AmmoController check for broken symlinks

We use AmmoController as a context manager for ammo in our tests. Add
logic to ensure errors are raised if it detects broken symlinks.

Adjust the couple of tests where we do actually expect to see broken
symlinks so they pass despite this.

test/common.py

@@ -36,7 +36,8 @@ class AmmoController:
     Ammo's configuration directory will be set up as AMMO_DIR,
     if it doesn't already exist.
 
-    Removes those folders on exit or error.
+    Removes those folders on exit or error. Raises AssertionError
+    after exit logic if there were broken symlinks.
     """
 
     def __init__(self):
@@ -57,11 +58,14 @@ def __exit__(self, *args, **kwargs):
         ammo instance. This ensures no reliance on a state
         created by a previous test.
         """
+        broken_symlinks = {}
         # remove symlinks
         for dirpath, _dirnames, filenames in os.walk(self.game.directory):
             for file in filenames:
                 full_path = Path(dirpath) / file
                 if full_path.is_symlink():
+                    if (dest := full_path.resolve()).exists() is False:
+                        broken_symlinks[str(full_path)] = str(dest)
                     full_path.unlink()
 
         # remove empty directories
@@ -82,6 +86,8 @@ def remove_empty_dirs(path):
         if AMMO_DIR.exists():
             shutil.rmtree(AMMO_DIR)
 
+        assert {} == broken_symlinks
+
 
 class FomodContextManager:
     def __init__(self, mod: Mod):

test/test_controller_instance.py

@@ -152,18 +152,19 @@ def test_controller_enabled_plugin_is_broken_symlink():
     Test that when an enabled plugin's symlink points at a non-existing file,
     the plugin is not shown.
     """
-    with AmmoController() as first_launch:
-        index = install_mod(first_launch, "conflict_1")
-        mod = first_launch.mods[index]
-        plugin = first_launch.plugins[0]
+    with pytest.raises(AssertionError):
+        with AmmoController() as first_launch:
+            index = install_mod(first_launch, "conflict_1")
+            mod = first_launch.mods[index]
+            plugin = first_launch.plugins[0]
 
-        file = [i for i in mod.files if i.name == "mock_plugin.esp"][0]
-        file.unlink()
+            file = [i for i in mod.files if i.name == "mock_plugin.esp"][0]
+            file.unlink()
 
-        with AmmoController() as controller:
-            mod = controller.mods[index]
-            assert mod.enabled is True
-            assert len(controller.plugins) == 0
+            with AmmoController() as controller:
+                mod = controller.mods[index]
+                assert mod.enabled is True
+                assert len(controller.plugins) == 0
 
 
 def test_controller_disabled_broken_mod_enabled_plugin():
@@ -206,13 +207,14 @@ def test_controller_missing_mod():
     found (because it was deleted from ammo's mod dir) isn't added
     to mods.
     """
-    with AmmoController() as first_launch:
-        index = install_mod(first_launch, "normal_mod")
-        mod = first_launch.mods[index]
-        shutil.rmtree(mod.location)
-
-        with AmmoController() as controller:
-            assert len(controller.mods) == 0
+    with pytest.raises(AssertionError):
+        with AmmoController() as first_launch:
+            index = install_mod(first_launch, "normal_mod")
+            mod = first_launch.mods[index]
+            shutil.rmtree(mod.location)
+
+            with AmmoController() as controller:
+                assert len(controller.mods) == 0
 
 
 def test_controller_plugin_without_mod():