wgsl-test

Test WGSL and WESL shaders with the CLI or vitest.

• Native WESL (@test) - Unit test shader functions, assertions run on GPU
• CLI (wgsl-test run) - Run tests from the command line
• TypeScript-driven - Integration tests, visual regression, custom validation

Installation

npm install wgsl-test

Native WESL Testing

Write tests directly in WESL with the @test attribute. Minimal boilerplate, assertions run on the GPU:

/// interp_test.wesl
import package::interp::smootherstep; // source fn to test
import wgsl_test::expectNear; // expectations from wgsl-test lib

@test  // tag each test fn
fn smootherstepQuarter() {
  expectNear(smootherstep(0.0, 1.0, 0.25), 0.103516);
}
...

CLI

Run tests directly from the command line:

wgsl-test run                      # discover **/*.test.wesl, run all
wgsl-test run path/to/test.wesl    # run specific file(s)
wgsl-test run --projectDir ./foo   # specify project root

Vitest Integration

Or run with a minimal TypeScript wrapper:

import { getGPUDevice, testWesl } from "wgsl-test";

const device = await getGPUDevice();

// runs all tests in interp_test
await testWesl({ device, moduleName: "interp_test" });

See API.md for assertion functions →

Visual Regression Testing

Test complete rendered images in vitest:

import { expectFragmentImage } from "wgsl-test";
import { imageMatcher } from "vitest-image-snapshot";

imageMatcher(); // Setup once

test("blur shader matches snapshot", async () => {
  await expectFragmentImage(device, "effects/blur.wgsl"); 
  // Snapshot automatically compared against __image_snapshots__/effects-blur.png
});

Update snapshots with vitest -u as needed.

See API.md for snapshot workflow and visual regression testing →

Testing Compute Shaders

For more control, use testCompute(). A test::results buffer is automatically provided:

import { testCompute, getGPUDevice } from "wgsl-test";

const device = await getGPUDevice();

const src = `
  import package::hash::lowbias32;

  @compute @workgroup_size(1)
  fn main() {
    test::results[0] = lowbias32(0u);
    test::results[1] = lowbias32(42u);
  }
`;

const result = await testCompute({ device, src, size: 2 });
// result = [0, 388445122]

See API.md for complete API documentation →

Testing Fragment Shaders

Some functions only make sense in fragment shaders.

Use testFragment() to test fragment shader rendering.

/// shaders/foo.wesl
fn bar(p: vec4f) -> vec4f {
  return 2 * sqrt(p);
}

const src = `
  @fragment
  fn fs_main(@builtin(position) pos:vec4f) -> @location(0) vec4f {
    return foo::bar(pos * 2);
  }
`;

const result = await testFragment({ device, src });
// result = [2.828, 1.414, 0.0, 2.0]  // vec4f color at pixel (0,0)

See API.md for derivatives, input textures, uniforms, and more →

API Documentation

• API.md - Complete API reference with detailed examples
• API.md#complete-test-example - Full vitest test setup with beforeAll/afterAll
• Examples - Tiny standalone examples

Future

File an issue or talk about your ideas on the tooling group discord chat.