Move pub/barback's Pool class into its own package.

pkg/pool/test/pool_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.
+
+import 'dart:async';
+
+import 'package:pool/pool.dart';
+import 'package:stack_trace/stack_trace.dart';
+import 'package:unittest/unittest.dart';
+
+void main() {
+  group("request()", () {
+    test("resources can be requested freely up to the limit", () {
+      var pool = new Pool(50);
+      var requests = [];
+      for (var i = 0; i < 50; i++) {
+        expect(pool.request(), completes);
+      }
+    });
+
+    test("resources block past the limit", () {
+      var pool = new Pool(50);
+      var requests = [];
+      for (var i = 0; i < 50; i++) {
+        expect(pool.request(), completes);
+      }
+      expect(pool.request(), doesNotComplete);
+    });
+
+    test("a blocked resource is allocated when another is released", () {
+      var pool = new Pool(50);
+      var requests = [];
+      for (var i = 0; i < 49; i++) {
+        expect(pool.request(), completes);
+      }
+
+      return pool.request().then((lastAllocatedResource) {
+        var blockedResource = pool.request();
+
+        return pumpEventQueue().then((_) {
+          lastAllocatedResource.release();
+          return pumpEventQueue();
+        }).then((_) {
+          expect(blockedResource, completes);
+        });
+      });
+    });
+  });
+
+  group("withResource()", () {
+    test("can be called freely up to the limit", () {
+      var pool = new Pool(50);
+      var requests = [];
+      for (var i = 0; i < 50; i++) {
+        pool.withResource(expectAsync(() => new Completer().future));
+      }
+    });
+
+    test("blocks the callback past the limit", () {
+      var pool = new Pool(50);
+      var requests = [];
+      for (var i = 0; i < 50; i++) {
+        pool.withResource(expectAsync(() => new Completer().future));
+      }
+      pool.withResource(expectNoAsync());
+    });
+
+    test("a blocked resource is allocated when another is released", () {
+      var pool = new Pool(50);
+      var requests = [];
+      for (var i = 0; i < 49; i++) {
+        pool.withResource(expectAsync(() => new Completer().future));
+      }
+
+      var completer = new Completer();
+      var lastAllocatedResource = pool.withResource(() => completer.future);
+      var blockedResourceAllocated = false;
+      var blockedResource = pool.withResource(() {
+        blockedResourceAllocated = true;
+      });
+
+      return pumpEventQueue().then((_) {
+        expect(blockedResourceAllocated, isFalse);
+        completer.complete();
+        return pumpEventQueue();
+      }).then((_) {
+        expect(blockedResourceAllocated, isTrue);
+      });
+    });
+  });
+
+  // TODO(nweiz): test timeouts when seaneagan's fake_async package lands.
+}
+
+/// Returns a [Future] that completes after pumping the event queue [times]
+/// times. By default, this should pump the event queue enough times to allow
+/// any code to run, as long as it's not waiting on some external event.
+Future pumpEventQueue([int times = 20]) {
+  if (times == 0) return new Future.value();
+  // We use a delayed future to allow microtask events to finish. The
+  // Future.value or Future() constructors use scheduleMicrotask themselves and
+  // would therefore not wait for microtask callbacks that are scheduled after
+  // invoking this method.
+  return new Future.delayed(Duration.ZERO, () => pumpEventQueue(times - 1));
+}
+
+/// Returns a function that will cause the test to fail if it's called.
+///
+/// This won't let the test complete until it's confident that the function
+/// won't be called.
+Function expectNoAsync() {
+  // Make sure the test lasts long enough for the function to get called if it's
+  // going to get called.
+  expect(pumpEventQueue(), completes);
+
+  var stack = new Trace.current(1);
+  return () => handleExternalError(
+      new TestFailure("Expected function not to be called."), "",
+      stack);
+}
+
+/// A matcher for Futures that asserts that they don't complete.
+///
+/// This won't let the test complete until it's confident that the function
+/// won't be called.
+Matcher get doesNotComplete => predicate((future) {
+  expect(future, new isInstanceOf<Future>('Future'));
+  // Make sure the test lasts long enough for the function to get called if it's
+  // going to get called.
+  expect(pumpEventQueue(), completes);
+
+  var stack = new Trace.current(1);
+  future.then((_) => handleExternalError(
+      new TestFailure("Expected future not to complete."), "",
+      stack));
+  return true;
+});