Add missing unit tests

packages/path_provider/test/path_provider_test.dart

@@ -33,29 +33,63 @@ void main() {
     expect(directory, isNull);
   });
 
-  test('getApplicationDocumentsDirectory test', () async {
+  test('getApplicationSupportDirectory test', () async {
     response = null;
-    final Directory directory = await getApplicationDocumentsDirectory();
+    final Directory directory = await getApplicationSupportDirectory();
     expect(
       log,
       <Matcher>[
-        isMethodCall('getApplicationDocumentsDirectory', arguments: null)
+        isMethodCall('getApplicationSupportDirectory', arguments: null)
       ],
     );
     expect(directory, isNull);
   });
 
+  test('getApplicationDocumentsDirectory test', () async {
+    response = null;
+    final Directory directory = await getApplicationDocumentsDirectory();
+    expect(
+      log,
+      <Matcher>[isMethodCall('getApplicationDocumentsDirectory', arguments: null)],
+    );
+    expect(directory, isNull);
+  });
+
+  test('getExternalStorageDirectory test', () async {
+    response = null;
+    final Directory directory = await getExternalStorageDirectory();
+    expect(
+      log,
+      <Matcher>[isMethodCall('getStorageDirectory', arguments: null)],
+    );
+    expect(directory, isNull);
+  });
+
   test('TemporaryDirectory path test', () async {
     final String fakePath = "/foo/bar/baz";
     response = fakePath;
     final Directory directory = await getTemporaryDirectory();
     expect(directory.path, equals(fakePath));
   });
 
+  test('ApplicationSupportDirectory path test', () async {
+    final String fakePath = "/foo/bar/baz";
+    response = fakePath;
+    final Directory directory = await getApplicationSupportDirectory();
+    expect(directory.path, equals(fakePath));
+  });
+
   test('ApplicationDocumentsDirectory path test', () async {
     final String fakePath = "/foo/bar/baz";
     response = fakePath;
     final Directory directory = await getApplicationDocumentsDirectory();
     expect(directory.path, equals(fakePath));
   });
+
+  test('ExternalStorageDirectory path test', () async {
+    final String fakePath = "/foo/bar/baz";
+    response = fakePath;
+    final Directory directory = await getExternalStorageDirectory();
+    expect(directory.path, equals(fakePath));
+  });
 }