Add a Cascade helper to Shelf.

pkg/shelf/test/cascade_test.dart

+// Copyright (c) 2014, 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 shelf.cascade_test;
+
+import 'package:shelf/shelf.dart';
+import 'package:shelf/src/util.dart';
+import 'package:unittest/unittest.dart';
+
+import 'test_util.dart';
+
+void main() {
+  group('a cascade with several handlers', () {
+    var handler;
+    setUp(() {
+      handler = new Cascade().add((request) {
+        if (request.headers['one'] == 'false') {
+          return new Response.notFound('handler 1');
+        } else {
+          return new Response.ok('handler 1');
+        }
+      }).add((request) {
+        if (request.headers['two'] == 'false') {
+          return new Response.notFound('handler 2');
+        } else {
+          return new Response.ok('handler 2');
+        }
+      }).add((request) {
+        if (request.headers['three'] == 'false') {
+          return new Response.notFound('handler 3');
+        } else {
+          return new Response.ok('handler 3');
+        }
+      }).handler;
+    });
+
+    test('the first response should be returned if it matches', () {
+      return makeSimpleRequest(handler).then((response) {
+        expect(response.statusCode, equals(200));
+        expect(response.readAsString(), completion(equals('handler 1')));
+      });
+    });
+
+    test("the second response should be returned if it matches and the first "
+        "doesn't", () {
+      return syncFuture(() {
+        return handler(new Request('GET', LOCALHOST_URI,
+            headers: {'one': 'false'}));
+      }).then((response) {
+        expect(response.statusCode, equals(200));
+        expect(response.readAsString(), completion(equals('handler 2')));
+      });
+    });
+
+    test("the third response should be returned if it matches and the first "
+        "two don't", () {
+      return syncFuture(() {
+        return handler(new Request('GET', LOCALHOST_URI,
+            headers: {'one': 'false', 'two': 'false'}));
+      }).then((response) {
+        expect(response.statusCode, equals(200));
+        expect(response.readAsString(), completion(equals('handler 3')));
+      });
+    });
+
+    test("the third response should be returned if no response matches", () {
+      return syncFuture(() {
+        return handler(new Request('GET', LOCALHOST_URI,
+            headers: {'one': 'false', 'two': 'false', 'three': 'false'}));
+      }).then((response) {
+        expect(response.statusCode, equals(404));
+        expect(response.readAsString(), completion(equals('handler 3')));
+      });
+    });
+  });
+
+  test('a 404 response triggers a cascade by default', () {
+    var handler = new Cascade()
+        .add((_) => new Response.notFound('handler 1'))
+        .add((_) => new Response.ok('handler 2'))
+        .handler;
+
+    return makeSimpleRequest(handler).then((response) {
+      expect(response.statusCode, equals(200));
+      expect(response.readAsString(), completion(equals('handler 2')));
+    });
+  });
+
+  test('a 405 response triggers a cascade by default', () {
+    var handler = new Cascade()
+        .add((_) => new Response(405))
+        .add((_) => new Response.ok('handler 2'))
+        .handler;
+
+    return makeSimpleRequest(handler).then((response) {
+      expect(response.statusCode, equals(200));
+      expect(response.readAsString(), completion(equals('handler 2')));
+    });
+  });
+
+  test('[statusCodes] controls which statuses cause cascading', () {
+    var handler = new Cascade(statusCodes: [302, 403])
+        .add((_) => new Response.found('/'))
+        .add((_) => new Response.forbidden('handler 2'))
+        .add((_) => new Response.notFound('handler 3'))
+        .add((_) => new Response.ok('handler 4'))
+        .handler;
+
+    return makeSimpleRequest(handler).then((response) {
+      expect(response.statusCode, equals(404));
+      expect(response.readAsString(), completion(equals('handler 3')));
+    });
+  });
+
+  test('[shouldCascade] controls which responses cause cascading', () {
+    var handler = new Cascade(
+          shouldCascade: (response) => response.statusCode % 2 == 1)
+        .add((_) => new Response.movedPermanently('/'))
+        .add((_) => new Response.forbidden('handler 2'))
+        .add((_) => new Response.notFound('handler 3'))
+        .add((_) => new Response.ok('handler 4'))
+        .handler;
+
+    return makeSimpleRequest(handler).then((response) {
+      expect(response.statusCode, equals(404));
+      expect(response.readAsString(), completion(equals('handler 3')));
+    });
+  });
+
+  group('errors', () {
+    test('getting the handler for an empty cascade fails', () {
+      expect(() => new Cascade().handler, throwsStateError);
+    });
+
+    test('passing [statusCodes] and [shouldCascade] at the same time fails',
+        () {
+      expect(() => new Cascade(
+            statusCodes: [404, 405], shouldCascade: (_) => false),
+          throwsArgumentError);
+    });
+  });
+}