test-grab

Test grab system (distance grab, one-hand grab, two-hand grab) against the grab example using the iwsdk CLI.

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Grab System Test

Run 5 test suites covering distance grab, one-hand grab, two-hand grab, system/component registration, and stability.

All tool calls go through npx iwsdk from the example workspace. The helper below keeps the existing MCP-style tool names, but it resolves them through iwsdk mcp inspect and then executes the matching CLI command directly.

Configuration:

EXAMPLE_DIR: /Users/felixz/Projects/immersive-web-sdk/examples/grab
ROOT: /Users/felixz/Projects/immersive-web-sdk

SHORTHAND: Throughout this document, MCPCALL means this shell function:

MCPCALL() {
  local tool=""
  local args=""
  local timeout=""
  while [ "$#" -gt 0 ]; do
    case "$1" in
      --tool) tool="$2"; shift 2 ;;
      --args) args="$2"; shift 2 ;;
      --timeout) timeout="$2"; shift 2 ;;
      *) echo "Unknown argument: $1" >&2; return 1 ;;
    esac
  done

  node --input-type=module - "$tool" "${args:-}" "${timeout:-}" <<'EOF'
import { spawnSync } from 'node:child_process';

const [toolName, rawArgs, timeout] = process.argv.slice(2);
const inspect = spawnSync('npx', ['iwsdk', 'mcp', 'inspect'], {
  cwd: process.cwd(),
  encoding: 'utf8',
});
if (inspect.status !== 0) {
  if (inspect.stderr) process.stderr.write(inspect.stderr);
  process.exit(inspect.status ?? 1);
}

const parsed = JSON.parse(inspect.stdout);
const tool = parsed.data.tools.find((entry) => entry.mcpName === toolName);
if (!tool) {
  console.error(`Unknown tool: ${toolName}`);
  process.exit(1);
}

const cliArgs = ['iwsdk', ...tool.cliPath.split(' ')];
if (rawArgs) cliArgs.push('--input-json', rawArgs);
if (timeout) cliArgs.push('--timeout', timeout);

const result = spawnSync('npx', cliArgs, {
  cwd: process.cwd(),
  encoding: 'utf8',
});
if (result.stdout) process.stdout.write(result.stdout);
if (result.stderr) process.stderr.write(result.stderr);
process.exit(result.status ?? 1);
EOF
}

Tool calling pattern: Every tool call is a Bash command using the MCPCALL shorthand:

MCPCALL --tool <TOOL_NAME> --args '<JSON_ARGS>' 2>/dev/null

<TOOL_NAME> uses MCP-style names (e.g. browser_reload_page, xr_accept_session, xr_look_at). The shell helper resolves them to direct CLI commands.
<JSON_ARGS> is a JSON object string. Omit --args if no arguments needed.
Output is JSON on stdout. Parse it to check assertions.
Use --timeout 20000 for operations that may take longer (reload, accept_session, animate_to, screenshot).
Running from the example workspace (or a child directory within it) is required so npx iwsdk can resolve the nearest IWSDK app root.

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 MCPCALL commands together.

IMPORTANT: When the instructions say "wait N seconds", use sleep N as a separate Bash command.

Step 1: Install Dependencies

cd /Users/felixz/Projects/immersive-web-sdk/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:

cd /Users/felixz/Projects/immersive-web-sdk/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; all subsequent MCPCALL commands resolve the active runtime through the CLI.

If the server fails to start within 60 seconds, report FAIL for all suites and skip to Step 5.

Step 3: Verify Connectivity

MCPCALL --tool ecs_list_systems 2>/dev/null

This must return JSON with a list of systems. If it fails:

Check the dev server output for errors
Try killing and restarting the server (Step 2)
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:

MCPCALL --tool browser_reload_page --timeout 20000 2>/dev/null Then: sleep 3
MCPCALL --tool xr_accept_session --timeout 20000 2>/dev/null Then: sleep 2
MCPCALL --tool browser_get_console_logs --args '{"count":20,"level":["error","warn"]}' 2>/dev/null Assert: No error-level logs.

Entity Discovery

Discover all grab entities dynamically:

MCPCALL --tool ecs_find_entities --args '{"withComponents":["DistanceGrabbable"]}' 2>/dev/null

Assert: At least 1 entity. Save first as <distance>.

MCPCALL --tool ecs_find_entities --args '{"withComponents":["OneHandGrabbable"]}' 2>/dev/null

Assert: At least 1 entity. Save first as <onehand>.

MCPCALL --tool ecs_find_entities --args '{"withComponents":["TwoHandsGrabbable"]}' 2>/dev/null

Assert: At least 1 entity. Save first as <twohand>.

Get entity positions via scene hierarchy:

MCPCALL --tool scene_get_hierarchy --args '{"maxDepth":3}' 2>/dev/null

Find Object3D UUIDs for each grab entity, then query their transforms:

MCPCALL --tool scene_get_object_transform --args '{"uuid":"<entity-uuid>"}' 2>/dev/null

Save positionRelativeToXROrigin as <distance-pos>, <onehand-pos>, <twohand-pos>.

Verify GrabSystem is active:

MCPCALL --tool ecs_list_systems 2>/dev/null

Assert: GrabSystem at priority -3.

Component Reference

Component	Pointer Type	Activation
`DistanceGrabbable`	Ray (trigger)	`xr_set_select_value`
`OneHandGrabbable`	Grip sphere (squeeze)	`xr_set_gamepad_state` button 1
`TwoHandsGrabbable`	Grip sphere (squeeze)	`xr_set_gamepad_state` button 1, both hands

Critical Distinction: Distance grab uses trigger (xr_set_select_value). One-hand and two-hand grab use squeeze (xr_set_gamepad_state button index 1). Wrong button silently fails.

Suite 1: Distance Grab (Ray + Trigger)

Test 1.1: Ray Hover

MCPCALL --tool xr_look_at --args '{"device":"controller-right","target":{"x":<distance-pos.x>,"y":<distance-pos.y>,"z":<distance-pos.z>},"moveToDistance":0.8}' 2>/dev/null

Then: sleep 1

MCPCALL --tool ecs_query_entity --args '{"entityIndex":<distance>,"components":["Hovered"]}' 2>/dev/null

Assert: Hovered present.

Test 1.2: Trigger to Grab

MCPCALL --tool ecs_snapshot --args '{"label":"before-grab"}' 2>/dev/null

MCPCALL --tool xr_set_select_value --args '{"device":"controller-right","value":1}' 2>/dev/null

Then: sleep 0.5

MCPCALL --tool ecs_query_entity --args '{"entityIndex":<distance>,"components":["Hovered","Pressed"]}' 2>/dev/null

Assert: Both Hovered and Pressed present.

Test 1.3: Move While Grabbed

MCPCALL --tool xr_animate_to --args '{"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

MCPCALL --tool ecs_snapshot --args '{"label":"after-move"}' 2>/dev/null

MCPCALL --tool ecs_diff --args '{"from":"before-grab","to":"after-move"}' 2>/dev/null

Assert: Entity's Transform.position must differ from initial.

Test 1.4: Release Trigger

MCPCALL --tool xr_set_select_value --args '{"device":"controller-right","value":0}' 2>/dev/null

Then: sleep 0.5

MCPCALL --tool ecs_query_entity --args '{"entityIndex":<distance>,"components":["Hovered","Pressed"]}' 2>/dev/null

Assert: Pressed removed. Handle persists (it's permanent).

Test 1.5: Point Away — Clean State

MCPCALL --tool xr_look_at --args '{"device":"controller-right","target":{"x":0,"y":1.6,"z":-5}}' 2>/dev/null

Then: sleep 1

MCPCALL --tool ecs_query_entity --args '{"entityIndex":<distance>,"components":["Hovered"]}' 2>/dev/null

Assert: Hovered removed.

Suite 2: One-Hand Grab (Squeeze)

Test 2.1: Ray Isolation — Ray Cannot Interact

MCPCALL --tool xr_look_at --args '{"device":"controller-right","target":{"x":<onehand-pos.x>,"y":<onehand-pos.y>,"z":<onehand-pos.z>},"moveToDistance":0.5}' 2>/dev/null

Then: sleep 1

MCPCALL --tool ecs_query_entity --args '{"entityIndex":<onehand>,"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

MCPCALL --tool xr_set_transform --args '{"device":"controller-right","position":{"x":<onehand-pos.x>,"y":<onehand-pos.y>,"z":<onehand-pos.z>},"orientation":{"pitch":0,"roll":0,"yaw":0}}' 2>/dev/null

MCPCALL --tool xr_set_gamepad_state --args '{"device":"controller-right","buttons":[{"index":1,"value":1,"touched":true}]}' 2>/dev/null

Then: sleep 0.5

MCPCALL --tool ecs_snapshot --args '{"label":"before-onehand"}' 2>/dev/null

Test 2.3: Move While Squeezing

MCPCALL --tool xr_animate_to --args '{"device":"controller-right","position":{"x":<onehand-pos.x>,"y":<onehand-pos.y + 0.3>,"z":<onehand-pos.z + 0.3>},"duration":1.0}' --timeout 20000 2>/dev/null

Then: sleep 1.5

MCPCALL --tool ecs_snapshot --args '{"label":"after-onehand-move"}' 2>/dev/null

MCPCALL --tool ecs_diff --args '{"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

MCPCALL --tool xr_set_gamepad_state --args '{"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

MCPCALL --tool xr_set_transform --args '{"device":"controller-left","position":{"x":<twohand-pos.x - 0.15>,"y":<twohand-pos.y>,"z":<twohand-pos.z>},"orientation":{"pitch":0,"roll":0,"yaw":0}}' 2>/dev/null

MCPCALL --tool xr_set_transform --args '{"device":"controller-right","position":{"x":<twohand-pos.x + 0.15>,"y":<twohand-pos.y>,"z":<twohand-pos.z>},"orientation":{"pitch":0,"roll":0,"yaw":0}}' 2>/dev/null

Test 3.2: Both Squeeze + Snapshot

MCPCALL --tool ecs_snapshot --args '{"label":"before-twohand"}' 2>/dev/null

MCPCALL --tool xr_set_gamepad_state --args '{"device":"controller-left","buttons":[{"index":1,"value":1,"touched":true}]}' 2>/dev/null

MCPCALL --tool xr_set_gamepad_state --args '{"device":"controller-right","buttons":[{"index":1,"value":1,"touched":true}]}' 2>/dev/null

Then: sleep 0.5

Test 3.3: Spread Hands — Scale Up

MCPCALL --tool xr_animate_to --args '{"device":"controller-left","position":{"x":<twohand-pos.x - 0.5>,"y":<twohand-pos.y>,"z":<twohand-pos.z>},"duration":1.0}' --timeout 20000 2>/dev/null

MCPCALL --tool xr_animate_to --args '{"device":"controller-right","position":{"x":<twohand-pos.x + 0.5>,"y":<twohand-pos.y>,"z":<twohand-pos.z>},"duration":1.0}' --timeout 20000 2>/dev/null

Then: sleep 1.5

MCPCALL --tool ecs_snapshot --args '{"label":"after-twohand-scale"}' 2>/dev/null

MCPCALL --tool ecs_diff --args '{"from":"before-twohand","to":"after-twohand-scale"}' 2>/dev/null

Assert: Entity Transform.scale should be larger than initial.

Test 3.4: Release Both

MCPCALL --tool xr_set_gamepad_state --args '{"device":"controller-left","buttons":[{"index":1,"value":0,"touched":false}]}' 2>/dev/null

MCPCALL --tool xr_set_gamepad_state --args '{"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

MCPCALL --tool ecs_list_systems 2>/dev/null

Assert: GrabSystem present at priority -3.

Test 4.2: Components Registered

MCPCALL --tool ecs_list_components 2>/dev/null

Assert: Must include: OneHandGrabbable, TwoHandsGrabbable, DistanceGrabbable, Handle.

Suite 5: Stability

MCPCALL --tool browser_get_console_logs --args '{"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:

cd /Users/felixz/Projects/immersive-web-sdk/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:

Stop the dev server: cd /Users/felixz/Projects/immersive-web-sdk/examples/grab && npx iwsdk dev down
Restart: re-run Step 2 to start a fresh dev server
Re-run the Pre-test Setup (reload, accept session)
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 ecs_snapshot/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 ecs_find_entities.

Repository: facebook/immersive-web-sdk
Commit: b3d1162

Last updated: 4 days ago
Created: 4 days ago

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