Add basic unit tests

test/api_test.dart

@@ -0,0 +1,56 @@
+import 'package:feet/api/api.dart';
+import 'package:flutter_test/flutter_test.dart';
+
+void main() {
+  group("API", () {
+    test("API key hashing", () {
+      final hash = FeverAPI.generateApiKey("bob", "abcdefgh");
+      expect(hash, "0fd86d2d609be5de9dce2ac77ad939a4");
+    });
+
+    test("API request builder", () {
+      final api = FeverAPI(apiUrl: "https://deez.org");
+
+      final item = Item(api,
+          id: 44,
+          feedId: 4,
+          title: "Morbius",
+          author: "Imposter from Among",
+          html: "<p>deez</p>",
+          url: "https://amogus.org",
+          isSaved: true,
+          isRead: false,
+          createdOnTime: DateTime.now());
+
+      final request = api
+          .request()
+          .withItems()
+          .withGroups()
+          .withFeeds()
+          .withFavicons()
+          .withIds([1, 2])
+          .sinceId(69)
+          .maxId(420)
+          .markItem(item, ItemMarkType.read);
+
+      expect(request.args, [
+        "items",
+        "groups",
+        "feeds",
+        "favicons",
+        "with_ids=1,2",
+        "since_id=69",
+        "max_id=420",
+        "mark=item",
+        "as=read",
+        "id=44",
+      ]);
+
+      expect(
+          request.generateUrl(),
+          Uri.parse("https://deez.org?api&items&groups&feeds&favicons&with_ids=1,2&since_id=69&max_id=420&mark=item&as=read&id=44"));
+    });
+
+    // TODO: Test item/feed/group/etc constructors
+  });
+}