WebNN Testing

This guide covers the testing methodologies and tools available for validating WebNN implementations across different browsers and devices.

Prerequisites

Before testing WebNN functionality, ensure you have properly configured your browser by following the WebNN Installation guide for your target backend (e.g., WebNN Windows ML / OpenVINO EP GPU).

Web Platform Tests (WPT) / Conformance Test Suite

The WebNN API follows W3C standards and includes comprehensive test suites to ensure cross-browser compatibility.

WebNN Web Platform Tests / Conformance Test Suite

The WebNN Conformance Test Suite (CTS)  is part of the web-platform-tests  project, a cross-browser test suite that ensures Web platform compatibility across all major browsers.

These tests provide confidence to:

• Browser implementers that their WebNN implementation is compatible with other browsers
• Web developers that they can rely on consistent WebNN behavior across browsers and devices

Web IDL Tests

File: idlharness.https.any.js

Validates that the WebNN API correctly implements the interfaces defined in the Web IDL specification. The test uses a daily-updated snapshot of the spec’s Web IDL located at ../interfaces/webnn.idl.

Validation Tests

Location: validation_tests/

These tests verify that WebNN methods properly validate input parameters according to the specification algorithms. They ensure invalid inputs are correctly rejected.

Example: validation_tests/matmul.https.any.js confirms that:

• Exceptions are thrown when input tensor ranks are less than 2
• Input tensor shapes must be broadcastable
• Other parameter validation requirements are met

Conformance Tests

Location: conformance_tests/

These tests verify that WebNN operators produce correct computational results.

Example: conformance_tests/matmul.https.any.js validates that N-dimensional matrix multiplication produces mathematically accurate outputs.

Test Execution Contexts

Device Variations

WebNN supports multiple compute devices (CPU, GPU, NPU). Tests use META: variant=?... to run the same test across different device types automatically.

Global Contexts

WebNN interfaces are available in both Window and Worker contexts via navigator.ml. Tests use:

• .any.js convention
• META: global=window,dedicatedworker

This allows the same test to run in multiple JavaScript execution contexts.

Note: Most operator-specific tests only specify global=window to reduce compute overhead, as behavior differences between contexts for individual operators are unlikely.

Running WPT Tests

WebNN Samples & Developer Preview Demos Testing

Interactive samples and demos help validate real-world WebNN usage patterns.

• W3C WebNN Samples  demonstrating practical WebNN API usage in web applications.
• WebNN Developer Preview Demos  showcases featuring WebNN API integration with ONNX Runtime Web.

Testing Sample and Demo Applications

An automated test framework is available for comprehensive sample testing:

Performance Testing

For comprehensive WebNN performance testing tools and Web AI benchmarking website, contact the Intel Web Team.

Additional Resources

• WebNN API Specification  - Complete technical specification
• Web Platform Tests  - Cross-browser testing initiative