Add error handling to directory

tests/standalone/src/io/DirectoryInvalidArgumentsTest.dart

Index: tests/standalone/src/io/DirectoryInvalidArgumentsTest.dart
diff --git a/tests/standalone/src/io/DirectoryInvalidArgumentsTest.dart b/tests/standalone/src/io/DirectoryInvalidArgumentsTest.dart
index 10c3ec0611af6dc76c8c28aaa389d4d455978241..c150369926878cd19238d350f1d17c13274bc839 100644
--- a/tests/standalone/src/io/DirectoryInvalidArgumentsTest.dart
+++ b/tests/standalone/src/io/DirectoryInvalidArgumentsTest.dart
@@ -20,18 +20,23 @@ class DirectoryInvalidArgumentsTest {
 
   static void testInvalidArguments() {
     Directory d = new Directory(12);
-    Expect.isFalse(d.existsSync());
+    try {
+      d.existsSync();
+      Expect.fail("No exception thrown");
+    } catch (var e) {
+      Expect.isTrue(e is IllegalArgumentException);
+    }
     try {
       d.deleteSync();
       Expect.fail("No exception thrown");
     } catch (var e) {
-      Expect.isTrue(e is DirectoryException);
+      Expect.isTrue(e is IllegalArgumentException);
     }
     try {
       d.createSync();
       Expect.fail("No exception thrown");
     } catch (var e) {
-      Expect.isTrue(e is DirectoryException);
+      Expect.isTrue(e is IllegalArgumentException);
     }
     testFailingList(d, false);
     d = new Directory(".");