rojo/.cursor/plans/two-way_sync_integration_tests_0e4e4dfc.plan.md

name	overview	todos	isProject
Two-way sync integration tests	Add integration tests covering the critical untested two-way sync operations: instance rename, ClassName transitions, non-Source property persistence, removal with meta cleanup, and end-to-end bidirectional sync workflows. Tests validate that the plugin sync pipeline can eventually replace `rojo syncback` for keeping the filesystem in sync with Studio.	id content status create-test-file Create tests/tests/two_way_sync.rs with test module structure, imports, and helper functions completed id content status register-module Register two_way_sync module in tests/end_to_end.rs completed id content status basic-source-write Test: update_source_writes_to_disk — verify Source property write to disk via InstanceUpdate completed id content status property-persistence Tests: update_non_source_property_creates_meta_file + update_properties_for_directory_script_writes_init_meta completed id content status rename-tests Tests: rename_standalone_script + rename_preserves_adjacent_meta_file completed id content status classname-tests Tests: classname_change_standalone_module_to_script + classname_change_directory_script_renames_init_file completed id content status removal-tests Tests: remove_instance_deletes_file_and_meta + remove_directory_instance completed id content status round-trip Test: round_trip_add_modify_rename_remove — end-to-end lifecycle completed id content status edge-cases Tests: property_update_skips_project_node_instances + echo_suppression_prevents_redundant_patches completed id content status ci-verify Run /ci to verify all new tests pass alongside existing 606+397 tests completed	false

Two-Way Sync Integration Tests

Intent

The plugin's two-way sync (POST /api/write) should eventually supersede the rojo syncback command entirely. The goal is continuous bidirectional sync: connect to Studio, accept changes, and work in an external IDE while others work in Studio. These tests validate the core primitives that make this possible.

Coverage Gaps Addressed

The existing tests cover format transitions (standalone/directory) and stress testing but have zero coverage for:

1. Instance rename (changed_name) — file/directory rename on disk, adjacent meta file rename
2. ClassName transitions (changed_class_name) — script type changes, init file detection in directories
3. Non-Source property persistence (changed_properties except Source) — writing to meta files
4. Instance removal with meta file cleanup — deleting files plus their adjacent .meta.json5
5. End-to-end round-trip — add instance, modify it, rename it, verify filesystem at each step

Test Fixture

Use existing syncback_write fixture (rojo-test/serve-tests/syncback_write/). It has a minimal project: ReplicatedStorage mapped to src/ with one existing existing.luau (ModuleScript). This is ideal for testing write operations without interference from complex file structures.

For rename tests, we also use syncback_format_transitions which has directory-format scripts with init files.

New Test File

Add tests to tests/tests/two_way_sync.rs (new file). Register it via tests/end_to_end.rs.

All tests follow the established pattern:

• run_serve_test(fixture_name, |session, _redactions| { ... })
• Find parent ID via get_api_rojo() + get_api_read()
• Construct WriteRequest with added, updated, or removed
• Call session.post_api_write()
• Assert filesystem state

Tests

1. update_source_writes_to_disk — Verify the basic Source write path

Send an InstanceUpdate with changed_properties: { Source: "-- new content" } for the existing existing.luau. Verify fs::read_to_string returns the new content. This is the most fundamental two-way sync operation.

2. update_non_source_property_creates_meta_file — Issue 2 coverage

Send an InstanceUpdate with a non-Source property (Attributes) for existing.luau. Verify:

• existing.meta.json5 is created adjacent to existing.luau
• The meta file contains the attribute value
• existing.luau itself is unchanged

3. update_properties_for_directory_script_writes_init_meta — Issue 2 directory path

Use syncback_format_transitions fixture. Send property update for a directory-format script (DirModuleWithChildren). Verify init.meta.json5 is created inside the directory.

4. rename_standalone_script — Issue 8 rename coverage

Add a new ModuleScript OldName via added, wait for it to appear on disk. Then send an InstanceUpdate with changed_name: Some("NewName"). Verify:

• OldName.luau is gone
• NewName.luau exists with same content

5. rename_preserves_adjacent_meta_file — Issue 8 meta rename

Add a ModuleScript, send a property update to create its meta file, then rename it. Verify both the .luau and .meta.json5 files are renamed together.

6. classname_change_standalone_module_to_script — Issue 8 ClassName coverage

Add a ModuleScript MyModule, then send changed_class_name: Some("Script"). Verify:

• MyModule.luau is gone
• MyModule.server.luau exists

7. classname_change_directory_script_renames_init_file — Issue 8 directory ClassName

Use syncback_format_transitions. Send changed_class_name for DirModuleWithChildren (ModuleScript -> Script). Verify:

• Directory still exists
• init.luau is gone
• init.server.luau exists
• Children still exist

8. remove_instance_deletes_file_and_meta — Issue 4 removal cleanup

Add a ModuleScript, create its meta file via property update, then remove it via removed. Verify both the .luau file and .meta.json5 are deleted.

9. remove_directory_instance — Issue 4 directory removal

Use syncback_format_transitions. Remove a directory-format instance. Verify the entire directory is deleted recursively.

10. round_trip_add_modify_rename_remove — End-to-end workflow

This test validates the complete lifecycle that makes two-way sync viable as a syncback replacement:

1. Add a new Script PlayerHandler with children
2. Verify directory created on disk
3. Modify its Source property
4. Verify file content updated
5. Rename it to GameHandler
6. Verify directory renamed
7. Remove it
8. Verify directory deleted

11. property_update_skips_project_node_instances — Post-fix coverage

Send property update for a Service (ReplicatedStorage) which has InstigatingSource::ProjectNode. Verify it does NOT corrupt the project file. The project file content should be unchanged.

12. echo_suppression_prevents_redundant_patches — Issue 7 coverage

Add a new instance, then immediately read the message queue. Count the WebSocket messages — there should be exactly one patch notification, not two (which would indicate echo from the VFS picking up the file write).

Key Implementation Details

• InstanceUpdate requires UstrMap<Option<Variant>> for changed_properties. Import rbx_dom_weak::{ustr, UstrMap}.
• Finding existing instance IDs: read tree via get_api_read(root_id), traverse instances to find by class/name.
• After post_api_write, sleep 200-500ms for change processor to handle VFS events.
• Use fs::read_to_string to verify file content, fs::metadata to verify existence.
• For rename/ClassName tests, the instance ID in InstanceUpdate must match the ID the server assigned (found via get_api_read after the initial add).

File Registration

Add mod two_way_sync; to tests/tests/mod.rs (or the test harness entry point tests/end_to_end.rs).