Start sketching out a buildAll() method.

pkg/barback/test/utils.dart

Index: pkg/barback/test/utils.dart
diff --git a/pkg/barback/test/utils.dart b/pkg/barback/test/utils.dart
index 99a7ec1d19d776d8101c08aeef52dc25a0a7bba2..365525b7c6d1d36be33697b8b6091eea6535b4fe 100644
--- a/pkg/barback/test/utils.dart
+++ b/pkg/barback/test/utils.dart
@@ -9,7 +9,6 @@ import 'dart:collection';
 import 'dart:io';
 
 import 'package:barback/barback.dart';
-import 'package:barback/src/asset_set.dart';
 import 'package:barback/src/cancelable_future.dart';
 import 'package:barback/src/utils.dart';
 import 'package:path/path.dart' as pathos;
@@ -223,6 +222,50 @@ void expectNoAsset(String name) {
   }, "get asset $name");
 }
 
+/// Schedules an expectation that the graph will output all of the given
+/// assets, and no others.
+///
+/// [assets] is a list of strings that can be parsed to [AssetID]s.
+void expectAllAssets(Iterable<String> assets) {
+  schedule(() {
+    return _barback.getAllAssets().then((actualAssets) {
+      var actualIds = actualAssets.map((asset) => asset.id).toSet();
+
+      for (var expected in assets) {
+        var id = new AssetId.parse(expected);

[nweiz, 2013/08/20 19:59:26]

Parse these outside of [schedule] so that parse errors will be reported
synchronously and you can include them in the schedule description.

[Bob Nystrom, 2013/08/20 21:29:20]

Done.

+        expect(actualIds, contains(id));
+        actualIds.remove(id);
+      }
+
+      expect(actualIds, isEmpty);
+    });
+  }, "get all assets");
+}
+
+/// Schedules an expectation that [Barback.getAllAssets] will return a [Future]
+/// that completes to a error that matches [match].
+///
+/// If [match] is a [List], then it expects the completed error to be an
+/// [AggregateException] whose errors match each matcher in the list. Otherwise,
+/// [match] should be a single matcher that the error should match.

[nweiz, 2013/08/20 19:59:26]

It seems weird to have a one-off special case for AggregateException. Eventually
we're going to want to start matching AggregateExceptions anywhere a
BarbackException might be thrown. It seems cleaner to create an
isAggregateException matcher.

That also makes this implementation a lot simpler:

    expect(_barback.getAllAssets(), throwsA(matcher))

[Bob Nystrom, 2013/08/20 21:29:20]

Done. The implementation of isAggregateError() feels a bit wonky, but I don't
have a good feel for when I should compose matchers versus actually just writing
a matcher class from scratch.

+void expectAllAssetsShouldFail(match) {
+  schedule(() {
+    return expect(_barback.getAllAssets().catchError((error) {

[nweiz, 2013/08/20 19:59:26]

Returning expect doesn't do anything.

[Bob Nystrom, 2013/08/20 21:29:20]

Done.

+      if (match is List) {
+        expect(error, new isInstanceOf<AggregateException>());
+        expect(error.errors.length, equals(match.length));
+        for (var matcher in match) {
+          expect(error.errors, contains(matcher));
+        }
+      } else {
+        expect(error, match);
+      }
+
+      throw error;
+    }), throwsA(new isInstanceOf<BarbackException>()));
+  }, "get all assets should fail");
+}
+
 /// Schedules an expectation that a [getAssetById] call for the given asset
 /// won't terminate at this point in the schedule.
 void expectAssetDoesNotComplete(String name) {