gpu.js/test/features/get-canvas.js

(function() {
  function getCanvasTest(mode ) {
    var gpu = new GPU();

    QUnit.assert.ok( gpu.getCanvas() === null, 'canvas is initially null');

    var render = gpu.createKernel(function() {
      this.color(0, 0, 0, 1);
    }, {
      output : [30,30],
      mode : mode
    }).setGraphical(true);

    QUnit.assert.ok( render !== null, 'function generated test');

    QUnit.assert.ok( render.getCanvas(), 'testing for canvas after createKernel' );
    QUnit.assert.ok( gpu.getCanvas(), 'testing for canvas after createKernel' );

    //
    // NOTE: GPU mode somehow return null when render()
    //
    QUnit.assert.ok( (r = render()) || true, 'rendering' );

    QUnit.assert.ok( render.getCanvas(), 'testing for canvas after render' );
    QUnit.assert.ok( gpu.getCanvas(), 'testing for canvas after render' );

  }

  QUnit.test( 'getCanvas (auto)', function() {
    getCanvasTest(null);
  });

  QUnit.test( 'getCanvas (gpu)', function() {
    getCanvasTest('gpu');
  });

  QUnit.test( 'getCanvas (webgl)', function() {
    getCanvasTest('webgl');
  });

  QUnit.test( 'getCanvas (webgl2)', function() {
    getCanvasTest('webgl2');
  });

  QUnit.test( 'getCanvas (CPU)', function() {
    getCanvasTest('cpu');
  });
})();