More test cases

test/iterable_extension_test.dart

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+import 'package:nc_photos/iterable_extension.dart';
+import 'package:test/test.dart';
+import 'package:tuple/tuple.dart';
+
+void main() {
+  group("IterableExtension", () {
+    test("sorted", () {
+      final src = [1, 4, 5, 2, 3, 8, 6, 7];
+      expect(src.sorted(), [1, 2, 3, 4, 5, 6, 7, 8]);
+    });
+
+    test("mapWithIndex", () {
+      final src = [1, 4, 5, 2, 3];
+      final result =
+          src.mapWithIndex((index, element) => Tuple2(index, element)).toList();
+      expect(result[0], Tuple2(0, 1));
+      expect(result[1], Tuple2(1, 4));
+      expect(result[2], Tuple2(2, 5));
+      expect(result[3], Tuple2(3, 2));
+      expect(result[4], Tuple2(4, 3));
+    });
+
+    test("containsIf", () {
+      final src = [
+        _ContainsIfTest(1),
+        _ContainsIfTest(4),
+        _ContainsIfTest(5),
+        _ContainsIfTest(2),
+        _ContainsIfTest(3),
+      ];
+      expect(src.containsIf(_ContainsIfTest(5), (a, b) => a.x == b.x), true);
+    });
+  });
+}
+
+class _ContainsIfTest {
+  _ContainsIfTest(this.x);
+
+  final int x;
+}

test/list_extension_test.dart

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+import 'package:nc_photos/list_extension.dart';
+import 'package:quiver/core.dart';
+import 'package:test/test.dart';
+
+void main() {
+  group("ListExtension", () {
+    group("distinct", () {
+      test("primitive", () {
+        expect([1, 2, 3, 4, 5, 3, 2, 4, 6].distinct(), [1, 2, 3, 4, 5, 6]);
+      });
+
+      test("class", () {
+        expect(
+            [
+              _DistinctTest(1, 1),
+              _DistinctTest(2, 2),
+              _DistinctTest(3, 3),
+              _DistinctTest(4, 4),
+              _DistinctTest(5, 4),
+              _DistinctTest(3, 6),
+              _DistinctTest(2, 2),
+              _DistinctTest(4, 8),
+              _DistinctTest(6, 9),
+            ].distinct(),
+            [
+              _DistinctTest(1, 1),
+              _DistinctTest(2, 2),
+              _DistinctTest(3, 3),
+              _DistinctTest(4, 4),
+              _DistinctTest(5, 4),
+              _DistinctTest(3, 6),
+              _DistinctTest(4, 8),
+              _DistinctTest(6, 9),
+            ]);
+      });
+    });
+
+    test("distinctIf", () {
+      expect(
+          [
+            _DistinctTest(1, 1),
+            _DistinctTest(2, 2),
+            _DistinctTest(3, 3),
+            _DistinctTest(4, 4),
+            _DistinctTest(5, 5),
+            _DistinctTest(3, 6),
+            _DistinctTest(2, 7),
+            _DistinctTest(4, 8),
+            _DistinctTest(6, 9),
+          ].distinctIf((a, b) => a.x == b.x, (a) => a.x),
+          [
+            _DistinctTest(1, 1),
+            _DistinctTest(2, 2),
+            _DistinctTest(3, 3),
+            _DistinctTest(4, 4),
+            _DistinctTest(5, 5),
+            _DistinctTest(6, 9),
+          ]);
+    });
+
+    test("takeIndex", () {
+      expect([1, 2, 3, 4, 5, 6].takeIndex([5, 4, 3, 1, 0]), [6, 5, 4, 2, 1]);
+    });
+  });
+}
+
+class _DistinctTest {
+  _DistinctTest(this.x, this.y);
+
+  @override
+  operator ==(Object other) =>
+      other is _DistinctTest && x == other.x && y == other.y;
+
+  @override
+  get hashCode => hash2(x, y);
+
+  @override
+  toString() => "{x: $x, y: $y}";
+
+  final int x;
+  final int y;
+}