Fix inconsistent arguments types in expectAsyncN methods.

pkg/unittest/lib/unittest.dart

 // Copyright (c) 2011, 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.
 
 /**
  * A library for writing dart unit tests.
  *
  * To import this library, use the pub package manager.
  * Create a pubspec.yaml file in your project and add
  * a dependency on unittest with the following lines:
@@ skipping 450 matching lines @@
 }
 
 /**
  * Indicate that [callback] is expected to be called a [count] number of times
  * (by default 1). The unittest framework will wait for the callback to run the
  * specified [count] times before it continues with the following test.  Using
  * [_expectAsync] will also ensure that errors that occur within [callback] are
  * tracked and reported. [callback] should take between 0 and 4 positional
  * arguments (named arguments are not supported here).
  */
-Function _expectAsync(Function callback, [int count = 1]) {
+Function _expectAsync(Function callback, {int count: 1}) {
   return new _SpreadArgsHelper.fixedCallCount(callback, count).invoke;
 }
 
 /**
  * Indicate that [callback] is expected to be called a [count] number of times
  * (by default 1). The unittest framework will wait for the callback to run the
  * specified [count] times before it continues with the following test.  Using
  * [expectAsync0] will also ensure that errors that occur within [callback] are
  * tracked and reported. [callback] should take 0 positional arguments (named
  * arguments are not supported).
  */
 // TODO(sigmund): deprecate this API when issue 2706 is fixed.
-Function expectAsync0(Function callback, [int count = 1]) {
+Function expectAsync0(Function callback, {int count: 1}) {
   return new _SpreadArgsHelper.fixedCallCount(callback, count).invoke0;
 }
 
 /** Like [expectAsync0] but [callback] should take 1 positional argument. */
 // TODO(sigmund): deprecate this API when issue 2706 is fixed.
 Function expectAsync1(Function callback, {int count: 1}) {
   return new _SpreadArgsHelper.fixedCallCount(callback, count).invoke1;
 }
 
 /** Like [expectAsync0] but [callback] should take 2 positional arguments. */
 // TODO(sigmund): deprecate this API when issue 2706 is fixed.
-Function expectAsync2(Function callback, [int count = 1]) {
+Function expectAsync2(Function callback, {int count: 1}) {
   return new _SpreadArgsHelper.fixedCallCount(callback, count).invoke2;
 }
 
 /**
  * Indicate that [callback] is expected to be called until [isDone] returns
  * true. The unittest framework checks [isDone] after each callback and only
  * when it returns true will it continue with the following test. Using
  * [expectAsyncUntil] will also ensure that errors that occur within
  * [callback] are tracked and reported. [callback] should take between 0 and
  * 4 positional arguments (named arguments are not supported).
@@ skipping 394 matching lines @@
 }
 
 /** Enable a test by ID. */
 void enableTest(int testId) => _setTestEnabledState(testId, true);
 
 /** Disable a test by ID. */
 void disableTest(int testId) => _setTestEnabledState(testId, false);
 
 /** Signature for a test function. */
 typedef void TestFunction();