Test grab system (distance grab, one-hand grab, two-hand grab) against the grab example using the iwsdk CLI.
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:
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.--timeout 20000 for operations that may take longer (reload, accept_session, animate_to, screenshot).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.
cd /Users/felixz/Projects/immersive-web-sdk/examples/grab && npm run fresh:install
Wait for this to complete before proceeding.
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.
MCPCALL --tool ecs_list_systems 2>/dev/null
This must return JSON with a list of systems. If it fails:
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.
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 | 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.
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.
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).
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
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.
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.
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.
If at any point a transient error occurs (server crash, WebSocket timeout, connection refused, etc.) that is NOT caused by a source code bug:
cd /Users/felixz/Projects/immersive-web-sdk/examples/grab && npx iwsdk dev downOnly give up after one retry attempt per suite. If the same suite fails twice, mark it FAIL and continue to the next suite.
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 is added by GrabSystem at init time and never removed. Grab state is tracked inside Handle.instance.outputState.
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.
The grab sphere intersector has a default radius of 7cm. Position the controller at the object's center for reliable detection.
Never cache entity indices across page reloads. Always re-discover via ecs_find_entities.