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packages/quiver/test/core/optional_test.dart

+// Copyright 2013 Google Inc. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+library quiver.core.optional_test;
+
+import 'package:quiver/core.dart';
+import 'package:test/test.dart';
+
+main() {
+  group('Optional', () {
+    test('absent should be not present and not gettable', () {
+      expect(new Optional<int>.absent().isPresent, isFalse);
+      expect(() => new Optional<int>.absent().value, throws);
+    });
+
+    test('of should return value', () {
+      expect(new Optional<int>.of(7).value, 7);
+    });
+
+    test('isPresent should execute only if present', () {
+      int value;
+      new Optional<int>.of(7).ifPresent((v) {
+        value = v;
+      });
+      expect(value, 7);
+      new Optional<int>.absent().ifPresent((v) {
+        value = v;
+      });
+      expect(value, 7);
+    });
+
+    test('isAbsent should execute only if absent', () {
+      int value;
+      new Optional<int>.of(7).ifAbsent(() {
+        value = 7;
+      });
+      expect(value, null);
+      new Optional<int>.absent().ifAbsent(() {
+        value = 7;
+      });
+      expect(value, 7);
+    });
+
+    test('fromNullable should allow present or absent', () {
+      expect(new Optional<int>.fromNullable(7).value, 7);
+      expect(new Optional<int>.fromNullable(null).isPresent, isFalse);
+    });
+
+    test('or should return present and replace absent', () {
+      expect(new Optional<int>.fromNullable(7).or(13), 7);
+      expect(new Optional<int>.fromNullable(null).or(13), 13);
+    });
+
+    test('orNull should return value if present or null if absent', () {
+      expect(new Optional<int>.fromNullable(7).orNull, isNotNull);
+      expect(new Optional<int>.fromNullable(null).orNull, isNull);
+    });
+
+    test('transform should return transformed value or absent', () {
+      expect(new Optional<int>.fromNullable(7).transform((a) => a + 1),
+          equals(new Optional<int>.of(8)));
+      expect(new Optional<int>.fromNullable(null)
+          .transform((a) => a + 1).isPresent, isFalse);
+    });
+
+    test('hashCode should allow optionals to be in hash sets', () {
+      expect(new Set.from([
+        new Optional<int>.of(7),
+        new Optional<int>.of(8),
+        new Optional<int>.absent()
+      ]), equals(new Set.from([
+        new Optional<int>.of(7),
+        new Optional<int>.of(8),
+        new Optional<int>.absent()
+      ])));
+      expect(new Set.from([
+        new Optional<int>.of(7),
+        new Optional<int>.of(8)
+      ]), isNot(equals(
+          new Set.from([new Optional<int>.of(7), new Optional<int>.of(9)]))));
+    });
+
+    test('== should compare by value', () {
+      expect(new Optional<int>.of(7), equals(new Optional<int>.of(7)));
+      expect(new Optional<int>.fromNullable(null),
+          equals(new Optional<int>.fromNullable(null)));
+      expect(new Optional<int>.fromNullable(null),
+          isNot(equals(new Optional<int>.of(7))));
+      expect(new Optional<int>.of(7), isNot(equals(new Optional<int>.of(8))));
+    });
+
+    test('toString should show the value or absent', () {
+      expect(
+          new Optional<int>.of(7).toString(), equals('Optional { value: 7 }'));
+      expect(new Optional<int>.fromNullable(null).toString(),
+          equals('Optional { absent }'));
+    });
+  });
+}