# Test Grab > Test grab system (distance grab, one-hand grab, two-hand grab) against the grab example using the iwsdk CLI. - Skill: `facebook/test-grab` (Agent Skill) - Install (CLI): `npx skillmds@latest add facebook/test-grab` - Raw SKILL.md: https://api.skillmd.com/api/skills/facebook/test-grab/raw - Safety review: pending - Works with: Claude Code, Claude.ai, OpenAI Codex - Category: Coding & Dev Tools - Author: facebook (https://skillmd.com/u/facebook) - Updated: 2026-09-17 - Page: https://skillmd.com/skills/facebook/test-grab --- # Grab System Test Run 5 test suites covering distance grab, one-hand grab, two-hand grab, system/component registration, and stability. **Configuration:** - EXAMPLE_DIR: `$IWSDK_REPO_ROOT/examples/grab` **Tool calls**: every tool call is `npx iwsdk [--input-json ''] [--timeout ]`, run from inside the example workspace (cwd `$EXAMPLE_DIR`). The CLI auto-discovers the IWSDK app root from cwd, so no path tricks are required. Run `npx iwsdk mcp inspect` from the example to discover available tools and their CLI subcommands. - `` is a JSON object string. Omit `--input-json` if no arguments are needed. - Output is JSON on stdout: `{ok, workspaceRoot, operation, result}`. Parse it to check assertions. - Use `--timeout 20000` for operations that may take longer (reload, xr enter, xr animate-to, screenshot). **IMPORTANT**: Run each Bash command one at a time. Parse the JSON output and verify assertions before moving to the next command. Do NOT chain multiple CLI commands together. **IMPORTANT**: When the instructions say "wait N seconds", use `sleep N` as a separate Bash command. --- ## Step 1: Install Dependencies ```bash cd $IWSDK_REPO_ROOT/examples/grab && npm run fresh:install ``` Wait for this to complete before proceeding. --- ## Step 2: Start Dev Server Start the dev server as a background task using the Bash tool's `run_in_background: true` parameter: ```bash cd $IWSDK_REPO_ROOT/examples/grab && npm run dev ``` **IMPORTANT**: This command MUST be run with `run_in_background: true` on the Bash tool — do NOT append `&` to the command itself. Once the background task is launched, poll the output for Vite's ready message (up to 60s). You can also run `npx iwsdk dev status` from the example directory until `state.running` becomes `true`. You do not need to extract or manage the port yourself; subsequent commands resolve the active runtime through the CLI automatically. If the server fails to start within 60 seconds, report FAIL for all suites and skip to Step 5. --- ## Step 3: Verify Connectivity ```bash npx iwsdk ecs systems 2>/dev/null ``` This must return JSON with a list of systems. If it fails: 1. Check the dev server output for errors 2. Try killing and restarting the server (Step 2) 3. If it still fails, report FAIL for all suites and skip to Step 5 --- ## Step 4: Run Test Suites ### Pre-test Setup Run these commands in order: 1. `npx iwsdk browser reload --timeout 20000 2>/dev/null` Then: `sleep 3` 2. `npx iwsdk xr enter --timeout 20000 2>/dev/null` Then: `sleep 2` 3. `npx iwsdk browser logs --input-json '{"count":20,"level":["error","warn"]}' 2>/dev/null` Assert: No error-level logs. ### Entity Discovery Discover all grab entities dynamically: ```bash npx iwsdk ecs find --input-json '{"withComponents":["DistanceGrabbable"]}' 2>/dev/null ``` Assert: At least 1 entity. Save first as ``. ```bash npx iwsdk ecs find --input-json '{"withComponents":["OneHandGrabbable"]}' 2>/dev/null ``` Assert: At least 1 entity. Save first as ``. ```bash npx iwsdk ecs find --input-json '{"withComponents":["TwoHandsGrabbable"]}' 2>/dev/null ``` Assert: At least 1 entity. Save first as ``. Get entity positions via scene hierarchy: ```bash npx iwsdk scene runtime-hierarchy --input-json '{"maxDepth":3}' 2>/dev/null ``` Find Object3D UUIDs for each grab entity, then query their transforms: ```bash npx iwsdk scene transform --input-json '{"uuid":""}' 2>/dev/null ``` Save `positionRelativeToXROrigin` as ``, ``, ``. Verify GrabSystem is active: ```bash npx iwsdk ecs systems 2>/dev/null ``` Assert: GrabSystem at priority -3. --- ### Component Reference | Component | Pointer Type | Activation | | ------------------- | --------------------- | ----------------------------------------------------- | | `DistanceGrabbable` | Ray (trigger) | `npx iwsdk xr set-select-value` | | `OneHandGrabbable` | Grip sphere (squeeze) | `npx iwsdk xr set-gamepad-state` button 1 | | `TwoHandsGrabbable` | Grip sphere (squeeze) | `npx iwsdk xr set-gamepad-state` button 1, both hands | **Critical Distinction**: Distance grab uses **trigger** (`npx iwsdk xr set-select-value`). One-hand and two-hand grab use **squeeze** (`npx iwsdk xr set-gamepad-state` button index 1). Wrong button silently fails. --- ### Suite 1: Distance Grab (Ray + Trigger) **Test 1.1: Ray Hover** ```bash npx iwsdk xr look-at --input-json '{"device":"controller-right","target":{"x":,"y":,"z":},"moveToDistance":0.8}' 2>/dev/null ``` Then: `sleep 1` ```bash npx iwsdk ecs query --input-json '{"entityIndex":,"components":["Hovered"]}' 2>/dev/null ``` Assert: `Hovered` present. **Test 1.2: Trigger to Grab** ```bash npx iwsdk ecs snapshot --input-json '{"label":"before-grab"}' 2>/dev/null ``` ```bash npx iwsdk xr set-select-value --input-json '{"device":"controller-right","value":1}' 2>/dev/null ``` Then: `sleep 0.5` ```bash npx iwsdk ecs query --input-json '{"entityIndex":,"components":["Hovered","Pressed"]}' 2>/dev/null ``` Assert: Both `Hovered` and `Pressed` present. **Test 1.3: Move While Grabbed** ```bash npx iwsdk xr animate-to --input-json '{"device":"controller-right","position":{"x":0.5,"y":1.5,"z":-1.0},"duration":1.0}' --timeout 20000 2>/dev/null ``` Then: `sleep 1.5` ```bash npx iwsdk ecs snapshot --input-json '{"label":"after-move"}' 2>/dev/null ``` ```bash npx iwsdk ecs diff --input-json '{"from":"before-grab","to":"after-move"}' 2>/dev/null ``` Assert: Entity's Transform.position must differ from initial. **Test 1.4: Release Trigger** ```bash npx iwsdk xr set-select-value --input-json '{"device":"controller-right","value":0}' 2>/dev/null ``` Then: `sleep 0.5` ```bash npx iwsdk ecs query --input-json '{"entityIndex":,"components":["Hovered","Pressed"]}' 2>/dev/null ``` Assert: `Pressed` removed. `Handle` persists (it's permanent). **Test 1.5: Point Away — Clean State** ```bash npx iwsdk xr look-at --input-json '{"device":"controller-right","target":{"x":0,"y":1.6,"z":-5}}' 2>/dev/null ``` Then: `sleep 1` ```bash npx iwsdk ecs query --input-json '{"entityIndex":,"components":["Hovered"]}' 2>/dev/null ``` Assert: `Hovered` removed. --- ### Suite 2: One-Hand Grab (Squeeze) **Test 2.1: Ray Isolation — Ray Cannot Interact** ```bash npx iwsdk xr look-at --input-json '{"device":"controller-right","target":{"x":,"y":,"z":},"moveToDistance":0.5}' 2>/dev/null ``` Then: `sleep 1` ```bash npx iwsdk ecs query --input-json '{"entityIndex":,"components":["Hovered","Pressed"]}' 2>/dev/null ``` Assert: No `Hovered` or `Pressed` on entity (ray is denied by `pointerEventsType`). **Test 2.2: Position Controller at Object + Squeeze** ```bash npx iwsdk xr set-transform --input-json '{"device":"controller-right","position":{"x":,"y":,"z":},"orientation":{"pitch":0,"roll":0,"yaw":0}}' 2>/dev/null ``` ```bash npx iwsdk xr set-gamepad-state --input-json '{"device":"controller-right","buttons":[{"index":1,"value":1,"touched":true}]}' 2>/dev/null ``` Then: `sleep 0.5` ```bash npx iwsdk ecs snapshot --input-json '{"label":"before-onehand"}' 2>/dev/null ``` **Test 2.3: Move While Squeezing** ```bash npx iwsdk xr animate-to --input-json '{"device":"controller-right","position":{"x":,"y":,"z":},"duration":1.0}' --timeout 20000 2>/dev/null ``` Then: `sleep 1.5` ```bash npx iwsdk ecs snapshot --input-json '{"label":"after-onehand-move"}' 2>/dev/null ``` ```bash npx iwsdk ecs diff --input-json '{"from":"before-onehand","to":"after-onehand-move"}' 2>/dev/null ``` Assert: Entity's Transform.position must have changed to follow the controller. **Test 2.4: Release Squeeze** ```bash npx iwsdk xr set-gamepad-state --input-json '{"device":"controller-right","buttons":[{"index":1,"value":0,"touched":false}]}' 2>/dev/null ``` Assert: Entity stops moving (Transform remains at released position). --- ### Suite 3: Two-Hand Grab (Both Controllers Squeeze) **Test 3.1: Position Both Controllers Near Object** ```bash npx iwsdk xr set-transform --input-json '{"device":"controller-left","position":{"x":,"y":,"z":},"orientation":{"pitch":0,"roll":0,"yaw":0}}' 2>/dev/null ``` ```bash npx iwsdk xr set-transform --input-json '{"device":"controller-right","position":{"x":,"y":,"z":},"orientation":{"pitch":0,"roll":0,"yaw":0}}' 2>/dev/null ``` **Test 3.2: Both Squeeze + Snapshot** ```bash npx iwsdk ecs snapshot --input-json '{"label":"before-twohand"}' 2>/dev/null ``` ```bash npx iwsdk xr set-gamepad-state --input-json '{"device":"controller-left","buttons":[{"index":1,"value":1,"touched":true}]}' 2>/dev/null ``` ```bash npx iwsdk xr set-gamepad-state --input-json '{"device":"controller-right","buttons":[{"index":1,"value":1,"touched":true}]}' 2>/dev/null ``` Then: `sleep 0.5` **Test 3.3: Spread Hands — Scale Up** ```bash npx iwsdk xr animate-to --input-json '{"device":"controller-left","position":{"x":,"y":,"z":},"duration":1.0}' --timeout 20000 2>/dev/null ``` ```bash npx iwsdk xr animate-to --input-json '{"device":"controller-right","position":{"x":,"y":,"z":},"duration":1.0}' --timeout 20000 2>/dev/null ``` Then: `sleep 1.5` ```bash npx iwsdk ecs snapshot --input-json '{"label":"after-twohand-scale"}' 2>/dev/null ``` ```bash npx iwsdk ecs diff --input-json '{"from":"before-twohand","to":"after-twohand-scale"}' 2>/dev/null ``` Assert: Entity Transform.scale should be larger than initial. **Test 3.4: Release Both** ```bash npx iwsdk xr set-gamepad-state --input-json '{"device":"controller-left","buttons":[{"index":1,"value":0,"touched":false}]}' 2>/dev/null ``` ```bash npx iwsdk xr set-gamepad-state --input-json '{"device":"controller-right","buttons":[{"index":1,"value":0,"touched":false}]}' 2>/dev/null ``` --- ### Suite 4: System & Component Registration **Test 4.1: GrabSystem at Correct Priority** ```bash npx iwsdk ecs systems 2>/dev/null ``` Assert: GrabSystem present at priority -3. **Test 4.2: Components Registered** ```bash npx iwsdk ecs components 2>/dev/null ``` Assert: Must include: `OneHandGrabbable`, `TwoHandsGrabbable`, `DistanceGrabbable`, `Handle`. --- ### Suite 5: Stability ```bash npx iwsdk browser logs --input-json '{"count":30,"level":["error","warn"]}' 2>/dev/null ``` Assert: No application-level errors or warnings. Pre-existing 404 resource errors from page load are acceptable. --- ## Step 5: Cleanup & Results Kill the dev server: ```bash cd $IWSDK_REPO_ROOT/examples/grab && npx iwsdk dev down ``` Output a summary table: ``` | Suite | Result | |-------------------------------|-----------| | 1. Distance Grab | PASS/FAIL | | 2. One-Hand Grab | PASS/FAIL | | 3. Two-Hand Grab | PASS/FAIL | | 4. System/Component Reg. | PASS/FAIL | | 5. Stability | PASS/FAIL | ``` If any suite fails, include which assertion failed and actual vs expected values. --- ## Recovery If at any point a transient error occurs (server crash, WebSocket timeout, connection refused, etc.) that is NOT caused by a source code bug: 1. Stop the dev server: `cd $IWSDK_REPO_ROOT/examples/grab && npx iwsdk dev down` 2. Restart: re-run Step 2 to start a fresh dev server 3. Re-run the Pre-test Setup (reload, accept session) 4. Retry the failed suite Only give up after one retry attempt per suite. If the same suite fails twice, mark it FAIL and continue to the next suite. --- ## Known Issues & Workarounds ### No Hovered/Pressed for near-field grabs OneHandGrabbable and TwoHandsGrabbable entities do NOT get `Hovered` or `Pressed` tags. Only distance grab (via ray) gets these tags. Use `npx iwsdk ecs snapshot`/`npx iwsdk ecs diff` to verify near-field grabs. ### Handle component is permanent `Handle` is added by `GrabSystem` at init time and never removed. Grab state is tracked inside `Handle.instance.outputState`. ### Trigger vs Squeeze confusion Distance grab uses **trigger** (`set_select_value`), not squeeze. One-hand and two-hand grab use **squeeze** (`set_gamepad_state` button index 1). Wrong button silently fails. ### Grab sphere radius is 0.07m The grab sphere intersector has a default radius of 7cm. Position the controller at the object's center for reliable detection. ### Entity indices change on reload Never cache entity indices across page reloads. Always re-discover via `npx iwsdk ecs find`.