[esnext] prototype runtime implementation for async functions

test/mjsunit/mjsunit.js

Index: test/mjsunit/mjsunit.js
diff --git a/test/mjsunit/mjsunit.js b/test/mjsunit/mjsunit.js
index 6a7c2da9e47d1ca56b52c98b3afbd2a2b6d72b6c..385d01484e74583bdcdf87dffe2d8a56ec1d8502 100644
--- a/test/mjsunit/mjsunit.js
+++ b/test/mjsunit/mjsunit.js
@@ -54,6 +54,7 @@ var assertSame;
 // and the properties of non-Array objects).
 var assertEquals;
 
+var assertEqualsAsync;
 
 // The difference between expected and found value is within certain tolerance.
 var assertEqualsDelta;
@@ -93,6 +94,8 @@ var assertNotNull;
 // to the type property on the thrown exception.
 var assertThrows;
 
+var assertThrowsAsync;
+
 // Assert that the passed function throws an exception.
 // The exception is checked against the second argument using assertEquals.
 var assertThrowsEquals;
@@ -286,6 +289,33 @@ var assertContains;
   };
 
 
+  assertEqualsAsync = function assertEqualsAsync(expected, run, msg) {
+    var actual;
+    var hadValue = false;
+    var hadError = false;
+    var promise = run();
+
+    if (typeof promise !== "object" || typeof promise.then !== "function") {
+      throw new MjsUnitAssertionError(
+          "Expected " + run.toString() +
+          " to return a Promise, but it returned " + PrettyPrint(promise));
+    }
+
+    promise.then(function(value) { hadValue = true; actual = value; },
+                 function(error) { hadError = true; actual = error; });
+
+    assertFalse(hadValue || hadError);
+
+    flushMicrotasks();
+
+    if (hadError) throw actual;
+
+    assertTrue(
+        hadValue, "Expected '" + run.toString() + "' to produce a value");
+
+    assertEquals(expected, actual, msg);
+  };
+
   assertEqualsDelta =
       function assertEqualsDelta(expected, found, delta, name_opt) {
     assertTrue(Math.abs(expected - found) <= delta, name_opt);
@@ -372,6 +402,40 @@ var assertContains;
     throw new MjsUnitAssertionError("Did not throw exception");
   };
 
+  assertThrowsAsync = function assertThrowsAsync(run, errorType, message) {
+    var actual;
+    var hadValue = false;
+    var hadError = false;
+    var promise = run();
+
+    if (typeof promise !== "object" || typeof promise.then !== "function") {
+      throw new MjsUnitAssertionError(
+          "Expected " + run.toString() +
+          " to return a Promise, but it returned " + PrettyPrint(promise));
+    }
+
+    promise.then(function(value) { hadValue = true; actual = value; },
+                 function(error) { hadError = true; actual = error; });
+
+    assertFalse(hadValue || hadError);
+
+    flushMicrotasks();
+
+    if (!hadError) {
+      throw new MjsUnitAssertionError(
+          "Expected " + run + "() to throw " + errorType.name +
+          ", but did not throw.");
+    }
+    if (!(actual instanceof errorType))
+      throw new MjsUnitAssertionError(
+          "Expected " + run + "() to throw " + errorType.name +
+          ", but threw '" + actual + "'");
+    if (message !== void 0 && actual.message !== message)
+      throw new MjsUnitAssertionError(
+          "Expected " + run + "() to throw '" + message + "', but threw '" +
+          actual.message + "'");
+  };
+
 
   assertThrowsEquals = function assertThrowsEquals(fun, val) {
     try {