Add package implementation.

test/no_package_info_test.dart

+// Copyright (c) 2016, 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.
+
+import 'package:test/test.dart';
+
+import 'package:package_resolver/package_resolver.dart';
+
+void main() {
+  var resolver;
+  setUp(() {
+    resolver = SyncPackageResolver.none;
+  });
+
+  test("exposes everything as null", () {
+    expect(resolver.packageConfigMap, isNull);
+    expect(resolver.packageConfigUri, isNull);
+    expect(resolver.packageRoot, isNull);
+    expect(resolver.processArgument, isNull);
+    expect(resolver.resolveUri("package:foo/bar.dart"), isNull);
+    expect(resolver.urlFor("foo"), isNull);
+    expect(resolver.urlFor("foo", "bar.dart"), isNull);
+    expect(resolver.packageUriFor("file:///foo/bar.dart"), isNull);
+    expect(resolver.packagePath("foo"), isNull);
+  });
+
+  group("resolveUri", () {
+    test("with an invalid argument type", () {
+      expect(() => resolver.resolveUri(12), throwsArgumentError);
+    });
+
+    test("with a non-package URI", () {
+      expect(() => resolver.resolveUri("file:///zip/zap"),
+          throwsFormatException);
+    });
+
+    test("with an invalid package URI", () {
+      expect(() => resolver.resolveUri("package:"), throwsFormatException);
+    });
+  });
+
+  test("packageUriFor with an invalid argument type", () {
+    expect(() => resolver.packageUriFor(12), throwsArgumentError);
+  });
+}