Physics System Test

Run 5 test suites covering gravity, static body verification, PhysicsBody state, 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/physics
• 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). 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, 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/physics && 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/physics && 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:

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. MCPCALL --tool browser_reload_page --timeout 20000 2>/dev/null Then: sleep 3

2. MCPCALL --tool xr_accept_session --timeout 20000 2>/dev/null Then: sleep 2

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

Verify Physics Setup

Find all physics bodies:

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

Assert: At least 1 entity.

For each entity found, query to identify dynamic vs static:

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

Check state field: "DYNAMIC" or "STATIC".

Save the dynamic entity as <sphere> and any static entity as <floor>.

Verify PhysicsSystem:

MCPCALL --tool ecs_list_systems 2>/dev/null

Assert: PhysicsSystem at priority -2, physicsEntities count >= 1.

Suite 1: Gravity — Dynamic Body Falls

Test 1.1: Verify Dynamic Entity Exists

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

Assert:

• state: "DYNAMIC"
• _engineBody: > 0 (Havok body created)
• gravityFactor: 1

Note: By the time you query, the sphere may have already fallen and come to rest.

Test 1.2: Deterministic Gravity Test

Reset the sphere position, then use pause/step to observe fall:

MCPCALL --tool ecs_pause 2>/dev/null

MCPCALL --tool ecs_set_component --args '{"entityIndex":<sphere>,"componentId":"Transform","field":"position","value":"[0, 3, -1.5]"}' 2>/dev/null

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

MCPCALL --tool ecs_step --args '{"count":50}' 2>/dev/null

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

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

Assert:

• Sphere's Transform.position[1] (Y) decreased from 3.0
• Only the dynamic sphere entity changed significantly

MCPCALL --tool ecs_resume 2>/dev/null

Suite 2: Static Body Doesn't Move

Test 2.1: Static Floor Stays Put

If a static entity was found during setup:

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

Assert:

• state: "STATIC"
• _linearVelocity: [0, 0, 0]
• _angularVelocity: [0, 0, 0]

Note: If no separate static PhysicsBody entity exists (environment geometry may not use PhysicsBody), skip this suite and report SKIP.

Suite 3: PhysicsBody State Values

Test 3.1: Inspect Dynamic Body Fields

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

Assert:

• state: "DYNAMIC"
• linearDamping: 0
• angularDamping: 0
• gravityFactor: 1
• _engineBody: > 0 (non-zero Havok handle)

Suite 4: System & Component Registration

Test 4.1: PhysicsSystem at Correct Priority

MCPCALL --tool ecs_list_systems 2>/dev/null

Assert:

• PhysicsSystem at priority -2
• Config keys: gravity

Test 4.2: Physics Components Registered

MCPCALL --tool ecs_list_components 2>/dev/null

Assert:

• PhysicsBody: state (Enum), linearDamping (Float32), angularDamping (Float32), gravityFactor (Float32), _linearVelocity (Vec3), _angularVelocity (Vec3), _engineBody (Float64)
• PhysicsShape: shape (Enum), dimensions (Vec3), density (Float32), restitution (Float32), friction (Float32), _engineShape (Float64)
• PhysicsManipulation: force (Vec3), linearVelocity (Vec3), angularVelocity (Vec3)

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/physics && npx iwsdk dev down

Output a summary table:

| Suite                     | Result         |
|---------------------------|----------------|
| 1. Gravity                | PASS/FAIL      |
| 2. Static Body            | PASS/FAIL/SKIP |
| 3. PhysicsBody State      | 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 /Users/felixz/Projects/immersive-web-sdk/examples/physics && 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

Sphere falls immediately

The dynamic sphere starts falling as soon as the Havok body is created. Use ecs_pause immediately after reload to catch it, or use the deterministic reset approach.

PhysicsManipulation is one-shot

PhysicsManipulation is automatically removed after forces are applied in a single frame. You cannot query it after processing.

ecs_set_component on Transform doesn't always override physics

While PhysicsSystem is running, it may overwrite your position on the next frame. Use ecs_pause before modifying positions.

Havok WASM initialization is async

Bodies may not be created on the first frame. The _engineBody field transitions from 0 to non-zero once Havok processes the entity.

Entity indices change on reload

Never cache entity indices across page reloads. Always re-discover via ecs_find_entities.