Merge main and resolve upstream integration conflicts

tests/common/test_command.py

@@ -16,6 +16,11 @@ from mvt.common.command import Command
 from mvt.common.config import settings
 from mvt.common.log import MVTLogHandler
 from mvt.common.module import EncryptedBackupError, MVTModule
+from unittest.mock import patch
+
+from click.testing import CliRunner
+
+from mvt.common.indicators import Indicators
 
 
 class RecordingModule(MVTModule):
@@ -50,6 +55,15 @@ class IndependentModule(RecordingModule):
     pass
 
 
+class URLRecordingModule(RecordingModule):
+    def collect_url_results(self):
+        self.add_url_result(
+            "https://example.org/message",
+            "2026-07-29 12:00:00.000000",
+            "test-chat",
+        )
+
+
 class CustomIOSBackupModule(RecordingModule):
     supported_commands = (("ios", "check-backup"),)
 
@@ -58,11 +72,132 @@ class CustomIOSFSModule(RecordingModule):
     supported_commands = (("ios", "check-fs"),)
 
 
+class UnscopedCustomModule(RecordingModule):
+    pass
+
+
 class CustomDependsOnBuiltin(RecordingModule):
     supported_commands = (("ios", "check-backup"),)
     dependencies = (FirstModule,)
 
 
+class ReplacementModule(FirstModule):
+    supported_commands = (("ios", "check-backup"),)
+    replaces = FirstModule
+
+    def run(self):
+        super().run()
+        self.results = ["replacement"]
+
+
+class OtherReplacementModule(FirstModule):
+    supported_commands = (("ios", "check-backup"),)
+    replaces = FirstModule
+
+
+class UnrelatedReplacementModule(RecordingModule):
+    supported_commands = (("ios", "check-backup"),)
+    replaces = IndependentModule
+
+
+class ReplacementOfReplacementModule(ReplacementModule):
+    supported_commands = (("ios", "check-backup"),)
+    replaces = ReplacementModule
+
+    def run(self):
+        super().run()
+        self.results = ["replacement of replacement"]
+
+
+class ReplacesOwnDependencyModule(FirstModule):
+    supported_commands = (("ios", "check-backup"),)
+    replaces = FirstModule
+    dependencies = (FirstModule,)
+
+
+class DisabledReplacementModule(FirstModule):
+    supported_commands = (("ios", "check-backup"),)
+    replaces = FirstModule
+    enabled = False
+
+
+class MutualReplacementOne(RecordingModule):
+    supported_commands = (("ios", "check-backup"),)
+
+
+class MutualReplacementTwo(RecordingModule):
+    supported_commands = (("ios", "check-backup"),)
+    replaces = MutualReplacementOne
+
+
+MutualReplacementOne.replaces = MutualReplacementTwo
+
+
+class CycleOneModule(RecordingModule):
+    supported_commands = (("ios", "check-backup"),)
+
+
+class CycleTwoModule(RecordingModule):
+    supported_commands = (("ios", "check-backup"),)
+    replaces = CycleOneModule
+
+
+class CycleThreeModule(RecordingModule):
+    supported_commands = (("ios", "check-backup"),)
+    replaces = CycleTwoModule
+
+
+CycleOneModule.replaces = CycleThreeModule
+
+
+class UnavailableDependencyModule(RecordingModule):
+    supported_commands = (("ios", "check-backup"),)
+
+
+class ReplacementMissingDependency(FirstModule):
+    supported_commands = (("ios", "check-backup"),)
+    replaces = FirstModule
+    dependencies = (UnavailableDependencyModule,)
+
+
+class SharedSlugModule(RecordingModule):
+    supported_commands = (("ios", "check-backup"),)
+    slug = "shared_slug"
+
+
+class OtherSharedSlugModule(RecordingModule):
+    supported_commands = (("ios", "check-backup"),)
+    slug = "shared_slug"
+
+
+class ReplacementKeepingTheSlug(FirstModule):
+    supported_commands = (("ios", "check-backup"),)
+    replaces = FirstModule
+    slug = "first_module"
+
+
+class SameNameReplacementModule(FirstModule):
+    supported_commands = (("ios", "check-backup"),)
+    replaces = FirstModule
+
+    def run(self):
+        super().run()
+        self.results = ["replacement"]
+
+
+# Modules replacing a built-in one usually keep its class name, which is the
+# name `--module` matches on.
+SameNameReplacementModule.__name__ = "FirstModule"
+
+
+def logged_substitutions(caplog) -> list[str]:
+    return [
+        record.getMessage()
+        for record in caplog.records
+        if record.levelno == logging.INFO and "replaces module" in record.getMessage()
+    ]
+
+
 class RecordingCommand(Command):
     def init(self):
         self.initialized = True
@@ -75,6 +210,86 @@ class RecordingCommand(Command):
 
 
 class TestCommand:
+    def test_listing_modules_does_not_load_indicators(self):
+        with patch("mvt.common.command.Indicators.load_indicators_files") as load:
+            cmd = RecordingCommand()
+            cmd.list_modules()
+            load.assert_not_called()
+
+    def test_output_folder_is_created_by_a_run_not_by_listing(self, tmp_path):
+        output_path = tmp_path / "out"
+        with patch("mvt.common.command.Indicators.load_indicators_files"):
+            cmd = RecordingCommand(results_path=str(output_path))
+            cmd.list_modules()
+            assert not output_path.exists()
+            cmd.run()
+        assert (output_path / "command.log").is_file()
+
+    def test_indicators_load_once_and_are_shared(self, indicator_file, monkeypatch):
+        from mvt.common.config import settings
+
+        monkeypatch.setattr(settings, "STIX2", "")
+        monkeypatch.setattr(Indicators, "_load_downloaded_indicators", lambda self: None)
+        original = Indicators.load_indicators_files
+        with patch.object(
+            Indicators, "load_indicators_files", autospec=True, side_effect=original
+        ) as load:
+            cmd = RecordingCommand(ioc_files=[indicator_file])
+            load.assert_not_called()
+            indicators = cmd.iocs
+            assert indicators.total_ioc_count == 9
+            assert len(indicators.ioc_collections) == 1
+            assert cmd.iocs is indicators
+            child = RecordingCommand(iocs=indicators)
+            assert child.iocs is indicators
+            load.assert_called_once_with(indicators, [indicator_file])
+
+    @pytest.mark.parametrize("assign", [False, True])
+    def test_supplied_empty_indicators_are_not_loaded(self, assign):
+        indicators = Indicators(logging.getLogger(__name__))
+        with patch.object(Indicators, "load_indicators_files") as load:
+            cmd = RecordingCommand(iocs=None if assign else indicators)
+            if assign:
+                cmd.iocs = indicators
+            assert cmd.iocs is indicators
+            assert cmd.iocs.total_ioc_count == 0
+            load.assert_not_called()
+
+    @pytest.mark.parametrize("list_modules", [False, True])
+    def test_backup_cli_does_not_load_indicators_before_analysis(
+        self, tmp_path, list_modules
+    ):
+        from mvt.ios.cli import check_backup
+
+        args = [str(tmp_path)]
+        if list_modules:
+            args.insert(0, "--list-modules")
+        with patch.object(Indicators, "load_indicators_files") as load:
+            result = CliRunner().invoke(check_backup, args)
+            assert result.exit_code == (0 if list_modules else 1)
+            load.assert_not_called()
+
+    def test_run_checks_synthetic_indicators(self, indicator_file, monkeypatch):
+        from mvt.common.config import settings
+
+        monkeypatch.setattr(settings, "STIX2", "")
+        monkeypatch.setattr(Indicators, "_load_downloaded_indicators", lambda self: None)
+
+        class MatchingModule(RecordingModule):
+            def run(self):
+                self.results = ["https://example.org/test"]
+
+            def check_indicators(self):
+                self.detected = [
+                    url for url in self.results if self.indicators.check_domain(url)
+                ]
+
+        cmd = RecordingCommand(ioc_files=[indicator_file])
+        cmd.modules = [MatchingModule]
+        cmd.run()
+        assert cmd.executed[0].detected == ["https://example.org/test"]
+        assert cmd.executed[0].indicators is cmd.iocs
+
     def setup_method(self):
         RecordingModule.run_order = []
 
@@ -100,6 +315,21 @@ class TestCommand:
 
         assert MVTModule._deduplicate_timeline(timeline) == timeline[:2]
 
+    def test_stores_collected_urls(self, tmp_path):
+        cmd = RecordingCommand(results_path=str(tmp_path))
+        cmd.modules = [URLRecordingModule]
+
+        cmd.run()
+
+        assert json.loads((tmp_path / "urls.json").read_text()) == [
+            {
+                "url": "https://example.org/message",
+                "expanded_url": None,
+                "timestamp": "2026-07-29 12:00:00.000000",
+                "source": "test-chat",
+            }
+        ]
+
     def test_modules_run_in_stable_topological_order(self):
         cmd = RecordingCommand(jobs=1)
         cmd.modules = [ThirdModule, IndependentModule, SecondModule, FirstModule]
@@ -178,7 +408,7 @@ class TestCommand:
         assert not hasattr(cmd, "initialized")
         assert "Circular module dependency detected" in caplog.text
 
-    def test_unavailable_dependency_warns_and_stops(self, caplog):
+    def test_unavailable_dependency_only_skips_the_dependent_module(self, caplog):
         class UnavailableModule(RecordingModule):
             pass
 
@@ -186,21 +416,108 @@ class TestCommand:
             dependencies = (UnavailableModule,)
 
         cmd = RecordingCommand()
-        cmd.modules = [DependentModule]
+        cmd.modules = [DependentModule, IndependentModule, FirstModule]
+
+        with caplog.at_level(logging.WARNING):
+            cmd.run()
+
+        assert RecordingModule.run_order == ["IndependentModule", "FirstModule"]
+        assert cmd.initialized
+        assert "Module DependentModule will be SKIPPED" in caplog.text
+        assert "depends on module UnavailableModule" in caplog.text
+
+    def test_modules_depending_on_a_skipped_module_are_skipped_too(self, caplog):
+        class UnavailableModule(RecordingModule):
+            pass
+
+        class SkippedModule(RecordingModule):
+            dependencies = (UnavailableModule,)
+
+        class DependsOnSkippedModule(RecordingModule):
+            dependencies = (SkippedModule,)
+
+        class DependsOnTheChain(RecordingModule):
+            dependencies = (DependsOnSkippedModule,)
+
+        cmd = RecordingCommand()
+        cmd.modules = [
+            DependsOnTheChain,
+            DependsOnSkippedModule,
+            SkippedModule,
+            IndependentModule,
+        ]
+
+        with caplog.at_level(logging.WARNING):
+            cmd.run()
+
+        assert RecordingModule.run_order == ["IndependentModule"]
+        skip_warnings = [
+            record.getMessage()
+            for record in caplog.records
+            if "will be SKIPPED" in record.getMessage()
+        ]
+        assert len(skip_warnings) == 3
+        assert [warning.split()[1] for warning in skip_warnings] == [
+            "SkippedModule",
+            "DependsOnSkippedModule",
+            "DependsOnTheChain",
+        ]
+        # Every warning names the root cause: the module missing a dependency
+        # and the dependency it is missing.
+        assert all("UnavailableModule" in warning for warning in skip_warnings)
+        assert all("module SkippedModule" in warning for warning in skip_warnings[1:])
+
+    def test_explicitly_selected_module_with_missing_dependency_runs_nothing(
+        self, caplog
+    ):
+        class UnavailableModule(RecordingModule):
+            pass
+
+        class DependentModule(RecordingModule):
+            dependencies = (UnavailableModule,)
+
+        cmd = RecordingCommand(module_name="DependentModule")
+        cmd.modules = [DependentModule, IndependentModule]
 
         with caplog.at_level(logging.WARNING):
             cmd.run()
 
         assert RecordingModule.run_order == []
-        assert not hasattr(cmd, "initialized")
-        assert "depends on unavailable module UnavailableModule" in caplog.text
+        assert "Module DependentModule will be SKIPPED" in caplog.text
+        assert "No modules will be run" in caplog.text
+        # Nothing else was selected, so the warning must not promise that the
+        # analysis continues right before saying that it does not.
+        assert "The rest of the analysis will still run" not in caplog.text
+
+    def test_unaffected_dependency_chains_keep_their_order(self, caplog):
+        class UnavailableModule(RecordingModule):
+            pass
+
+        class SkippedModule(RecordingModule):
+            dependencies = (UnavailableModule,)
+
+        cmd = RecordingCommand()
+        cmd.modules = [ThirdModule, SkippedModule, SecondModule, FirstModule]
+
+        with caplog.at_level(logging.WARNING):
+            cmd.run()
+
+        assert RecordingModule.run_order == [
+            "FirstModule",
+            "SecondModule",
+            "ThirdModule",
+        ]
 
     def test_custom_modules_are_filtered_before_ordering(self):
         cmd = RecordingCommand()
         cmd.platform = "ios"
         cmd.name = "check-backup"
         cmd.modules = [FirstModule]
-        cmd.custom_modules = [CustomIOSBackupModule, CustomIOSFSModule]
+        cmd.custom_modules = [
+            CustomIOSBackupModule,
+            CustomIOSFSModule,
+            UnscopedCustomModule,
+        ]
 
         assert [module.__name__ for module in cmd._ordered_modules()] == [
             "FirstModule",
@@ -460,3 +777,375 @@ class TestCommand:
 
         assert run_order == ["one", "two"]
         assert "forcing sequential module execution" in caplog.text
+    def test_custom_module_replaces_builtin(self, caplog):
+        cmd = RecordingCommand()
+        cmd.platform = "ios"
+        cmd.name = "check-backup"
+        cmd.modules = [FirstModule, IndependentModule]
+        cmd.custom_modules = [ReplacementModule]
+
+        with caplog.at_level(logging.INFO):
+            cmd.run()
+
+        assert RecordingModule.run_order == ["IndependentModule", "ReplacementModule"]
+        assert cmd.module_replacements == {FirstModule: ReplacementModule}
+        assert (
+            "Module ReplacementModule from" in caplog.text
+            and "replaces module FirstModule" in caplog.text
+        )
+
+    def test_modules_without_replaces_all_run(self):
+        cmd = RecordingCommand()
+        cmd.platform = "ios"
+        cmd.name = "check-backup"
+        cmd.modules = [FirstModule]
+        cmd.custom_modules = [CustomIOSBackupModule]
+
+        cmd.run()
+
+        assert RecordingModule.run_order == ["FirstModule", "CustomIOSBackupModule"]
+        assert cmd.module_replacements == {}
+
+    def test_unavailable_replaced_module_is_ignored(self, caplog):
+        cmd = RecordingCommand()
+        cmd.platform = "ios"
+        cmd.name = "check-backup"
+        cmd.modules = [IndependentModule]
+        cmd.custom_modules = [ReplacementModule]
+
+        with caplog.at_level(logging.INFO):
+            cmd.run()
+
+        assert RecordingModule.run_order == ["IndependentModule", "ReplacementModule"]
+        assert cmd.module_replacements == {}
+        assert "replaces module FirstModule" not in caplog.text
+
+    def test_dependencies_are_resolved_to_the_replacement(self):
+        cmd = RecordingCommand()
+        cmd.platform = "ios"
+        cmd.name = "check-backup"
+        cmd.modules = [SecondModule, FirstModule]
+        cmd.custom_modules = [ReplacementModule]
+
+        cmd.run()
+
+        assert RecordingModule.run_order == ["ReplacementModule", "SecondModule"]
+        second = next(
+            module for module in cmd.executed if isinstance(module, SecondModule)
+        )
+        assert isinstance(second.dependency_modules[FirstModule], ReplacementModule)
+        assert second.results == ["replacement", "second"]
+
+    def test_replacement_with_unavailable_dependency_skips_its_dependents(
+        self, caplog
+    ):
+        cmd = RecordingCommand()
+        cmd.platform = "ios"
+        cmd.name = "check-backup"
+        cmd.modules = [FirstModule, SecondModule, IndependentModule]
+        cmd.custom_modules = [ReplacementMissingDependency]
+
+        with caplog.at_level(logging.INFO):
+            cmd.run()
+
+        # The replacement cannot run, and the module it replaced was dropped
+        # from the run by the replacement, so neither of them produces
+        # results and the module depending on the replaced one is skipped.
+        assert RecordingModule.run_order == ["IndependentModule"]
+        assert (
+            "Module ReplacementMissingDependency will be SKIPPED: it depends "
+            "on module UnavailableDependencyModule, which is not available in "
+            "this command." in caplog.text
+        )
+        # The skipped dependent is told which module it actually depends on,
+        # and the module class its author declared.
+        assert (
+            "Module SecondModule will be SKIPPED: it depends on module "
+            "ReplacementMissingDependency (replacing module FirstModule), "
+            "itself skipped for depending on unavailable module "
+            "UnavailableDependencyModule." in caplog.text
+        )
+
+    def test_selected_replacement_with_unavailable_dependency_runs_nothing(
+        self, caplog, tmp_path
+    ):
+        cmd = RecordingCommand(module_name="FirstModule", results_path=str(tmp_path))
+        cmd.platform = "ios"
+        cmd.name = "check-backup"
+        cmd.modules = [FirstModule, IndependentModule]
+        cmd.custom_modules = [ReplacementMissingDependency]
+
+        with caplog.at_level(logging.INFO):
+            cmd.run()
+
+        assert RecordingModule.run_order == []
+        assert not hasattr(cmd, "initialized")
+        assert (
+            "Module FirstModule was replaced by module "
+            "ReplacementMissingDependency, which is run in its place."
+            in caplog.text
+        )
+        assert "Module ReplacementMissingDependency will be SKIPPED" in caplog.text
+        assert "No modules will be run" in caplog.text
+        # Nothing else was selected, so the warnings must not promise that the
+        # analysis continues right before saying that it does not.
+        assert "The rest of the analysis will still run" not in caplog.text
+        # No module ran, so no results were stored next to the command log.
+        assert [path.name for path in tmp_path.iterdir()] == ["command.log"]
+
+    def test_chained_replacements_are_resolved(self):
+        cmd = RecordingCommand()
+        cmd.platform = "ios"
+        cmd.name = "check-backup"
+        cmd.modules = [SecondModule, FirstModule]
+        cmd.custom_modules = [ReplacementModule, ReplacementOfReplacementModule]
+
+        cmd.run()
+
+        assert RecordingModule.run_order == [
+            "ReplacementOfReplacementModule",
+            "SecondModule",
+        ]
+        second = next(
+            module for module in cmd.executed if isinstance(module, SecondModule)
+        )
+        assert second.results == ["replacement of replacement", "second"]
+
+    def test_replacement_which_is_not_a_subclass_warns(self, caplog):
+        cmd = RecordingCommand()
+        cmd.platform = "ios"
+        cmd.name = "check-backup"
+        cmd.modules = [IndependentModule]
+        cmd.custom_modules = [UnrelatedReplacementModule]
+
+        with caplog.at_level(logging.WARNING):
+            cmd.run()
+
+        assert RecordingModule.run_order == ["UnrelatedReplacementModule"]
+        assert "is not a subclass of it" in caplog.text
+
+    def test_multiple_modules_replacing_the_same_module_warn(self, caplog):
+        cmd = RecordingCommand()
+        cmd.platform = "ios"
+        cmd.name = "check-backup"
+        cmd.modules = [FirstModule]
+        cmd.custom_modules = [ReplacementModule, OtherReplacementModule]
+
+        with caplog.at_level(logging.WARNING):
+            cmd.run()
+
+        assert RecordingModule.run_order == [
+            "ReplacementModule",
+            "OtherReplacementModule",
+        ]
+        assert cmd.module_replacements == {FirstModule: ReplacementModule}
+        assert (
+            "Modules ReplacementModule and OtherReplacementModule both replace "
+            "module FirstModule. Both of them will run, FirstModule will not, "
+            "and modules depending on FirstModule will use the results of "
+            "ReplacementModule." in caplog.text
+        )
+        assert "overwrite each other's results file" in caplog.text
+
+    def test_module_replacing_its_own_dependency_runs(self, caplog):
+        cmd = RecordingCommand()
+        cmd.platform = "ios"
+        cmd.name = "check-backup"
+        cmd.modules = [FirstModule]
+        cmd.custom_modules = [ReplacesOwnDependencyModule]
+
+        with caplog.at_level(logging.WARNING):
+            cmd.run()
+
+        assert RecordingModule.run_order == ["ReplacesOwnDependencyModule"]
+        assert (
+            "Module ReplacesOwnDependencyModule depends on module FirstModule, "
+            "which it also replaces" in caplog.text
+        )
+
+    def test_literal_self_dependency_is_still_circular(self, caplog):
+        class SelfDependentModule(RecordingModule):
+            pass
+
+        SelfDependentModule.dependencies = (SelfDependentModule,)
+
+        cmd = RecordingCommand()
+        cmd.modules = [SelfDependentModule]
+
+        with caplog.at_level(logging.WARNING):
+            cmd.run()
+
+        assert RecordingModule.run_order == []
+        assert not hasattr(cmd, "initialized")
+        assert "Circular module dependency detected" in caplog.text
+
+    def test_disabled_replacement_keeps_the_replaced_module(self, caplog):
+        cmd = RecordingCommand()
+        cmd.platform = "ios"
+        cmd.name = "check-backup"
+        cmd.modules = [FirstModule]
+        cmd.custom_modules = [DisabledReplacementModule]
+
+        with caplog.at_level(logging.INFO):
+            cmd.run()
+
+        assert RecordingModule.run_order == ["FirstModule"]
+        assert cmd.module_replacements == {}
+        assert logged_substitutions(caplog) == []
+
+    def test_modules_replacing_each_other_all_run(self, caplog):
+        cmd = RecordingCommand()
+        cmd.platform = "ios"
+        cmd.name = "check-backup"
+        cmd.custom_modules = [MutualReplacementOne, MutualReplacementTwo]
+
+        with caplog.at_level(logging.INFO):
+            cmd.run()
+
+        assert RecordingModule.run_order == [
+            "MutualReplacementOne",
+            "MutualReplacementTwo",
+        ]
+        assert cmd.module_replacements == {}
+        assert (
+            "Modules MutualReplacementOne, MutualReplacementTwo replace each "
+            "other in a cycle" in caplog.text
+        )
+        assert logged_substitutions(caplog) == []
+
+    def test_replacement_cycle_of_three_modules_all_run(self, caplog):
+        cmd = RecordingCommand()
+        cmd.platform = "ios"
+        cmd.name = "check-backup"
+        cmd.custom_modules = [CycleOneModule, CycleTwoModule, CycleThreeModule]
+
+        with caplog.at_level(logging.INFO):
+            cmd.run()
+
+        assert RecordingModule.run_order == [
+            "CycleOneModule",
+            "CycleTwoModule",
+            "CycleThreeModule",
+        ]
+        assert cmd.module_replacements == {}
+        assert (
+            "Modules CycleOneModule, CycleThreeModule, CycleTwoModule replace "
+            "each other in a cycle" in caplog.text
+        )
+        assert logged_substitutions(caplog) == []
+
+    def test_selected_replaced_module_name_runs_the_replacement(self, caplog):
+        cmd = RecordingCommand(module_name="FirstModule")
+        cmd.platform = "ios"
+        cmd.name = "check-backup"
+        cmd.modules = [FirstModule]
+        cmd.custom_modules = [ReplacementModule]
+
+        with caplog.at_level(logging.INFO):
+            cmd.run()
+
+        assert RecordingModule.run_order == ["ReplacementModule"]
+        assert (
+            "Module FirstModule was replaced by module ReplacementModule"
+            in caplog.text
+        )
+
+    def test_unknown_selected_module_warns_and_stops(self, caplog):
+        cmd = RecordingCommand(module_name="NoSuchModule")
+        cmd.name = "check-backup"
+        cmd.modules = [FirstModule]
+
+        with caplog.at_level(logging.WARNING):
+            cmd.run()
+
+        assert RecordingModule.run_order == []
+        assert not hasattr(cmd, "initialized")
+        assert (
+            "No module named NoSuchModule is available for the check-backup "
+            "command" in caplog.text
+        )
+
+    def test_selected_module_name_matches_the_replacement(self):
+        cmd = RecordingCommand(module_name="FirstModule")
+        cmd.platform = "ios"
+        cmd.name = "check-backup"
+        cmd.modules = [FirstModule]
+        cmd.custom_modules = [SameNameReplacementModule]
+
+        cmd.run()
+
+        assert len(cmd.executed) == 1
+        assert isinstance(cmd.executed[0], SameNameReplacementModule)
+        assert cmd.executed[0].results == ["replacement"]
+
+    def test_list_modules_reflects_replacements(self, caplog):
+        cmd = RecordingCommand()
+        cmd.platform = "ios"
+        cmd.name = "check-backup"
+        cmd.modules = [FirstModule, IndependentModule]
+        cmd.custom_modules = [ReplacementModule]
+
+        with caplog.at_level(logging.INFO):
+            cmd.list_modules()
+
+        listed = [
+            record.getMessage()
+            for record in caplog.records
+            if "Modules from" in record.getMessage()
+        ]
+        assert any("ReplacementModule" in message for message in listed)
+        assert not any("FirstModule" in message for message in listed)
+
+    def test_modules_sharing_a_slug_are_reported(self, caplog):
+        cmd = RecordingCommand()
+        cmd.platform = "ios"
+        cmd.name = "check-backup"
+        cmd.custom_modules = [SharedSlugModule, OtherSharedSlugModule]
+
+        with caplog.at_level(logging.WARNING):
+            cmd.run()
+
+        assert RecordingModule.run_order == [
+            "SharedSlugModule",
+            "OtherSharedSlugModule",
+        ]
+        collisions = [
+            record.getMessage()
+            for record in caplog.records
+            if "both use the slug" in record.getMessage()
+        ]
+        assert len(collisions) == 1
+        assert "Modules SharedSlugModule from" in collisions[0]
+        assert "and OtherSharedSlugModule from" in collisions[0]
+        assert "both use the slug shared_slug" in collisions[0]
+        assert "overwrites the results of the other in shared_slug.json" in (
+            collisions[0]
+        )
+
+    def test_replacement_keeping_the_replaced_slug_is_not_reported(self, caplog):
+        cmd = RecordingCommand()
+        cmd.platform = "ios"
+        cmd.name = "check-backup"
+        cmd.modules = [FirstModule]
+        cmd.custom_modules = [ReplacementKeepingTheSlug]
+
+        with caplog.at_level(logging.WARNING):
+            cmd.run()
+
+        # The replaced module is no longer part of the run, so taking over its
+        # slug is what the replacement is for, not a collision.
+        assert RecordingModule.run_order == ["ReplacementKeepingTheSlug"]
+        assert ReplacementKeepingTheSlug.get_slug() == FirstModule.get_slug()
+        assert "both use the slug" not in caplog.text
+
+    def test_modules_with_distinct_slugs_are_not_reported(self, caplog):
+        cmd = RecordingCommand()
+        cmd.platform = "ios"
+        cmd.name = "check-backup"
+        cmd.modules = [FirstModule, IndependentModule]
+        cmd.custom_modules = [CustomIOSBackupModule]
+
+        with caplog.at_level(logging.WARNING):
+            cmd.run()
+
+        assert "both use the slug" not in caplog.text