test js promises

tests/misc/coroutines/src/Main.hx

@@ -1,5 +1,8 @@
 function main() {
 	utest.UTest.run([
 		new TestStaticFields(),
+		#if js
+		new TestJsPromise(),
+		#end
 	]);
 }

tests/misc/coroutines/src/TestJsPromise.hx

@@ -0,0 +1,48 @@
+import js.lib.Promise;
+
+@:coroutine
+private function await<T>(p:Promise<T>):T {
+	return Coroutine.suspend(cont -> p.then(cont));
+}
+
+private function promise<T>(c:Coroutine<()->T>):Promise<T> {
+	return new Promise((resolve,_) -> c.start(resolve));
+}
+
+class TestJsPromise extends utest.Test {
+	function testAwait(async:Async) {
+		var p = Promise.resolve(41);
+
+		@:coroutine function awaiting() {
+			var x = await(p);
+			return x + 1;
+		}
+
+		awaiting.start(result -> {
+			Assert.equals(42, result);
+			async.done();
+		});
+	}
+
+	function testPromise(async:Async) {
+		var p = promise(() -> 42);
+		p.then(result -> {
+			Assert.equals(42, result);
+			async.done();
+		});
+	}
+
+	function testAsyncAwait(async:Async) {
+		var p1 = Promise.resolve(41);
+
+		var p2 = promise(() -> {
+			var x = await(p1);
+			return x + 1;
+		});
+
+		p2.then(result -> {
+			Assert.equals(42, result);
+			async.done();
+		});
+	}
+}