Migrate language/arithmetic2_test ... language/async_await_syntax_test.

tests/language_strong/assert_with_message_test.dart

-// Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
-// for details. All rights reserved. Use of this source code is governed by a
-// BSD-style license that can be found in the LICENSE file.
-
-import "package:expect/expect.dart";
-
-main() {
-  var assertsEnabled = false;
-  assert((assertsEnabled = true));
-  if (!assertsEnabled) return;
-
-  // TODO(rnystrom): Test cases where the first argument to assert() is a
-  // function.
-
-  testAssertFails();
-  testAssertDoesNotFail();
-  testNullMessage();
-  testDoesNotEvaluateMessageIfAssertSucceeds();
-  testMessageExpressionThatThrows();
-  testCallsToStringOnMessageLazily();
-}
-
-/// A class with a custom toString() that tracks when it is called.
-class ToString {
-  bool calledToString = false;
-
-  String toString() {
-    calledToString = true;
-    return "toString!";
-  }
-}
-
-testAssertFails() {
-  try {
-    assert(false, "Oops");
-    Expect.fail("Assert should throw.");
-  } catch (e) {
-    Expect.isTrue(e.toString().contains("Oops"));
-  }
-}
-
-testAssertDoesNotFail() {
-  try {
-    assert(true, "Oops");
-  } catch (e) {
-    Expect.fail("Assert should not throw.");
-  }
-}
-
-testNullMessage() {
-  try {
-    assert(false, null);
-    Expect.fail("Assert should throw.");
-  } catch (e) {
-    Expect.isTrue(e.toString().contains("is not true"));
-  }
-}
-
-testDoesNotEvaluateMessageIfAssertSucceeds() {
-  try {
-    var evaluated = false;
-    assert(true, evaluated = true);
-    Expect.isFalse(evaluated);
-  } catch (e) {
-    Expect.fail("Assert should not throw.");
-  }
-}
-
-testMessageExpressionThatThrows() {
-  try {
-    assert(false, throw "dang");
-    Expect.fail("Should throw");
-  } catch (e) {
-    Expect.equals(e, "dang");
-  }
-}
-
-testCallsToStringOnMessageLazily() {
-  var toString = new ToString();
-  try {
-    assert(false, toString);
-    Expect.fail("Assert should throw.");
-  } catch (e) {
-    Expect.isFalse(toString.calledToString);
-    Expect.isTrue(e.toString().contains("Instance of 'ToString'"));
-    Expect.isFalse(toString.calledToString);
-  }
-}