Add immediate size validation tests for pipeline layout creation.

src/webgpu/api/validation/createPipelineLayout.spec.ts

@@ -6,7 +6,8 @@ TODO: review existing tests, write descriptions, and make sure tests are complet
 
 import { AllFeaturesMaxLimitsGPUTest } from '../.././gpu_test.js';
 import { makeTestGroup } from '../../../common/framework/test_group.js';
-import { count, range } from '../../../common/util/util.js';
+import { getGPU } from '../../../common/util/navigator_gpu.js';
+import { count, range, supportsImmediateData } from '../../../common/util/util.js';
 import {
   bufferBindingTypeInfo,
   getBindingLimitForBindingType,
@@ -512,3 +513,54 @@ g.test('bind_group_layouts,set_pipeline_with_null_bind_group_layouts')
       }
     }
   });
+
+g.test('immediate_data_size')
+  .desc(
+    `
+    Test that creating a pipeline layout with immediateSize validates:
+    - immediateSize must be a multiple of 4.
+    - immediateSize must be <= device.limits.maxImmediateSize.
+  `
+  )
+  .params(u => {
+    const validImmediateSizes = [0, 4, 'max'] as const;
+    const invalidAlignmentImmediateSizes = [1, 2, 3, 5] as const;
+    const invalidRangeImmediateSizes = ['exceedLimit'] as const;
+    return u.combine('immediateSize', [
+      ...validImmediateSizes,
+      ...invalidAlignmentImmediateSizes,
+      ...invalidRangeImmediateSizes,
+    ] as const);
+  })
+  .fn(t => {
+    t.skipIf(!supportsImmediateData(getGPU(t.rec)), 'Immediate data not supported');
+
+    const maxImmediateSize = t.device.limits.maxImmediateSize!;
+
+    const { immediateSize: sizeVariant } = t.params;
+    let size: number;
+    switch (sizeVariant) {
+      case 'max':
+        size = maxImmediateSize;
+        break;
+      case 'exceedLimit':
+        size = maxImmediateSize + 4;
+        break;
+      default:
+        size = sizeVariant;
+        break;
+    }
+
+    const descriptor = {
+      bindGroupLayouts: [],
+      immediateSize: size,
+    };
+
+    const isMultipleOf4 = size % 4 === 0;
+    const isWithinLimit = size <= maxImmediateSize;
+    const shouldSucceed = isMultipleOf4 && isWithinLimit;
+
+    t.expectValidationError(() => {
+      t.device.createPipelineLayout(descriptor);
+    }, !shouldSucceed);
+  });