[test] Add js-api tests (WebAssembly#114)

This tests the `WebAssembly.Memory` constructor and the `grow` method.

* Memory.buffer should be frozen and not extensible when shared
* Don't check isFrozen during grow (constructor test is sufficient)
* Don't check stray argument in shared memory detach test

test/js-api/memory/constructor.any.js

@@ -8,15 +8,18 @@ function assert_Memory(memory, expected) {
 
   // https://github.com/WebAssembly/spec/issues/840
   assert_equals(memory.buffer, memory.buffer, "buffer should be idempotent");
-  assert_equals(Object.getPrototypeOf(memory.buffer), ArrayBuffer.prototype,
-                "prototype of buffer");
-  assert_true(Object.isExtensible(memory.buffer), "buffer extensibility");
+  const isShared = !!expected.shared;
+  const bufferType = isShared ? self.SharedArrayBuffer : ArrayBuffer;
+  assert_equals(Object.getPrototypeOf(memory.buffer), bufferType.prototype,
+                'prototype of buffer');
   assert_equals(memory.buffer.byteLength, 0x10000 * expected.size, "size of buffer");
   if (expected.size > 0) {
     const array = new Uint8Array(memory.buffer);
     assert_equals(array[0], 0, "first element of buffer");
     assert_equals(array[array.byteLength - 1], 0, "last element of buffer");
   }
+  assert_equals(isShared, Object.isFrozen(memory.buffer), "buffer frozen");
+  assert_not_equals(Object.isExtensible(memory.buffer), isShared, "buffer extensibility");
 }
 
 test(() => {
@@ -83,6 +86,10 @@ test(() => {
   assert_throws(new RangeError(), () => new WebAssembly.Memory({ "initial": 10, "maximum": 9 }));
 }, "Initial value exceeds maximum");
 
+test(() => {
+  assert_throws(new TypeError(), () => new WebAssembly.Memory({ "initial": 10, "shared": true }));
+}, "Shared memory without maximum");
+
 test(() => {
   const proxy = new Proxy({}, {
     has(o, x) {
@@ -118,13 +125,25 @@ test(() => {
         },
       };
     },
+
+    get shared() {
+      order.push("shared");
+      return {
+        valueOf() {
+          order.push("shared valueOf");
+          return true;
+        },
+      };
+    },
   });
 
   assert_array_equals(order, [
     "initial",
     "initial valueOf",
     "maximum",
     "maximum valueOf",
+    "shared",
+    "shared valueOf",
   ]);
 }, "Order of evaluation for descriptor");
 
@@ -145,3 +164,9 @@ test(() => {
   const memory = new WebAssembly.Memory(argument, {});
   assert_Memory(memory, { "size": 0 });
 }, "Stray argument");
+
+test(() => {
+  const argument = { "initial": 4, "maximum": 10, shared: true };
+  const memory = new WebAssembly.Memory(argument);
+  assert_Memory(memory, { "size": 4, "shared": true });
+}, "Shared memory");

test/js-api/memory/grow.any.js

@@ -2,7 +2,8 @@
 
 function assert_ArrayBuffer(actual, expected, message) {
   // https://github.com/WebAssembly/spec/issues/840
-  assert_equals(Object.getPrototypeOf(actual), ArrayBuffer.prototype,
+  const bufferType = expected.shared ? self.SharedArrayBuffer : ArrayBuffer;
+  assert_equals(Object.getPrototypeOf(actual), bufferType.prototype,
                 `${message}: prototype`);
   if (expected.detached) {
     // https://github.com/tc39/ecma262/issues/678
@@ -183,3 +184,29 @@ test(() => {
   assert_ArrayBuffer(oldMemory, { "detached": true }, "Old buffer after growing");
   assert_ArrayBuffer(newMemory, { "size": 2 }, "New buffer after growing");
 }, "Stray argument");
+
+test(() => {
+  const argument = { "initial": 1, "maximum": 2, "shared": true };
+  const memory = new WebAssembly.Memory(argument);
+  const oldMemory = memory.buffer;
+  assert_ArrayBuffer(oldMemory, { "size": 1, "shared": true }, "Buffer before growing");
+
+  const result = memory.grow(1);
+  assert_equals(result, 1);
+
+  const newMemory = memory.buffer;
+  assert_not_equals(oldMemory, newMemory);
+  assert_ArrayBuffer(oldMemory, { "size": 1, "shared": true }, "Old buffer after growing");
+  assert_ArrayBuffer(newMemory, { "size": 2, "shared": true }, "New buffer after growing");
+
+  // The old and new buffers must have the same value for the
+  // [[ArrayBufferData]] internal slot.
+  const oldArray = new Uint8Array(oldMemory);
+  const newArray = new Uint8Array(newMemory);
+  assert_equals(oldArray[0], 0, "old first element");
+  assert_equals(newArray[0], 0, "new first element");
+  oldArray[0] = 1;
+  assert_equals(oldArray[0], 1, "old first element");
+  assert_equals(newArray[0], 1, "new first element");
+
+}, "Growing shared memory does not detach old buffer");