Refactor the barback tests somewhat.

pkg/barback/test/asset_set_test.dart

 // Copyright (c) 2013, 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.
 
 library barback.test.asset_set_test;
 
 import 'dart:async';
 import 'dart:io';
 
 import 'package:barback/barback.dart';
 import 'package:barback/src/asset_set.dart';
 import 'package:unittest/unittest.dart';
 
 import 'utils.dart';
 
 main() {
   initConfig();
 
   var fooId = new AssetId.parse("app|foo.txt");
   var barId = new AssetId.parse("app|bar.txt");
+  var bazId = new AssetId.parse("app|baz.txt");
+
+  group(".from()", () {
+    test("creates a set from an iterable", () {
+      var set = new AssetSet.from([
+        new Asset.fromString(fooId, "foo"),
+        new Asset.fromString(barId, "bar")
+      ]);
+
+      expect(set.containsId(fooId), isTrue);
+      expect(set.containsId(barId), isTrue);
+      expect(set.containsId(bazId), isFalse);
+    });
+  });
 
   group("[] operator", () {
     test("gets an asset with the given ID", () {
       var set = new AssetSet();
-      var foo = new MockAsset(fooId, "foo");
+      var foo = new Asset.fromString(fooId, "foo");
       set.add(foo);
 
       expect(set[fooId], equals(foo));
     });
 
     test("returns null if no asset with the ID is in the set", () {
       var set = new AssetSet();
       expect(set[fooId], isNull);
     });
   });
 
   group(".add()", () {
     test("adds the asset to the set", () {
       var set = new AssetSet();
-      var foo = new MockAsset(fooId, "foo");
+      var foo = new Asset.fromString(fooId, "foo");
       set.add(foo);
       expect(set.contains(foo), isTrue);
     });
 
     test("replaces a previously added asset with that ID", () {
       var set = new AssetSet();
-      set.add(new MockAsset(fooId, "before"));
-      set.add(new MockAsset(fooId, "after"));
-      expect(set[fooId].contents, equals("after"));
+      set.add(new Asset.fromString(fooId, "before"));
+      set.add(new Asset.fromString(fooId, "after"));
+      expect(set[fooId].readAsString(), completion(equals("after")));
     });
 
     test("returns the added item", () {
       var set = new AssetSet();
-      var foo = new MockAsset(fooId, "foo");
+      var foo = new Asset.fromString(fooId, "foo");
       expect(set.add(foo), equals(foo));
     });
   });
 
   group(".addAll()", () {
     test("adds the assets to the set", () {
       var set = new AssetSet();
-      var foo = new MockAsset(fooId, "foo");
-      var bar = new MockAsset(barId, "bar");
+      var foo = new Asset.fromString(fooId, "foo");
+      var bar = new Asset.fromString(barId, "bar");
       set.addAll([foo, bar]);
       expect(set.contains(foo), isTrue);
       expect(set.contains(bar), isTrue);
     });
 
     test("replaces assets earlier in the sequence with later ones", () {
       var set = new AssetSet();
-      var foo1 = new MockAsset(fooId, "before");
-      var foo2 = new MockAsset(fooId, "after");
+      var foo1 = new Asset.fromString(fooId, "before");
+      var foo2 = new Asset.fromString(fooId, "after");
       set.addAll([foo1, foo2]);
-      expect(set[fooId].contents, equals("after"));
+      expect(set[fooId].readAsString(), completion(equals("after")));
     });
   });
 
   group(".clear()", () {
     test("empties the set", () {
       var set = new AssetSet();
-      var foo = new MockAsset(fooId, "foo");
+      var foo = new Asset.fromString(fooId, "foo");
       set.add(foo);
       set.clear();
 
       expect(set.length, equals(0));
       expect(set.contains(foo), isFalse);
     });
   });
 
   group(".contains()", () {
     test("returns true if the asset is in the set", () {
       var set = new AssetSet();
-      var foo = new MockAsset(fooId, "foo");
-      var bar = new MockAsset(barId, "bar");
+      var foo = new Asset.fromString(fooId, "foo");
+      var bar = new Asset.fromString(barId, "bar");
       set.add(foo);
 
       expect(set.contains(foo), isTrue);
       expect(set.contains(bar), isFalse);
     });
   });
 
   group(".containsId()", () {
     test("returns true if an asset with the ID is in the set", () {
       var set = new AssetSet();
-      var foo = new MockAsset(fooId, "foo");
+      var foo = new Asset.fromString(fooId, "foo");
       set.add(foo);
 
       expect(set.containsId(fooId), isTrue);
       expect(set.containsId(barId), isFalse);
     });
   });
+
+  group(".removeId()", () {
+    test("removes the asset with the ID from the set", () {
+      var set = new AssetSet();
+      var foo = new Asset.fromString(fooId, "foo");
+      set.add(foo);
+
+      set.removeId(fooId);
+      expect(set.containsId(fooId), isFalse);
+    });
+
+    test("returns the removed asset", () {
+      var set = new AssetSet();
+      var foo = new Asset.fromString(fooId, "foo");
+      set.add(foo);
+
+      expect(set.removeId(fooId).readAsString(), completion(equals("foo")));
+    });
+
+    test("returns null when removing an asset not in the set", () {
+      var set = new AssetSet();
+      var foo = new Asset.fromString(fooId, "foo");
+      set.add(foo);
+
+      expect(set.removeId(barId), isNull);
+    });
+  });
 }