feat: Add dependency injection to make testing easier

lib/models/get_song_bpm_model.dart

@@ -18,8 +18,14 @@ class GetSongBPMModel {
     'Accept': 'application/json',
   };
 
+  // dependency injection of http client
+  late http.Client client;
+  GetSongBPMModel(http.Client client) {
+    this.client = client;
+  }
+
   // getSongs : Returns a list of songs with a given BPM.
-  static Future<List<TempoSong>> getSongs(int bpm) async {
+  Future<List<TempoSong>> getSongs(int bpm) async {
     log("Getting songs of BPM $bpm");
     final queryParams = {
       "api_key": Config.getSongBpmApiKey,

lib/models/spotify_controller_model.dart

@@ -15,6 +15,7 @@ import 'package:spotify_sdk/models/connection_status.dart';
 import 'package:spotify_sdk/models/image_uri.dart';
 import 'package:spotify_sdk/models/player_state.dart';
 import 'package:spotify_sdk/spotify_sdk.dart';
+import 'package:http/http.dart' as http;
 
 // SpotifyControllerModel is in charge of maintaining connection between
 // the app and the Spotify app, as well as for managing the player.
@@ -59,7 +60,9 @@ class SpotifyControllerModel with ChangeNotifier {
   String _cadenceValue = "-";
   String _cadenceStatus = "Inactive";
 
-  SpotifyControllerModel(this._ctx) {
+  // http client for fetching (dependency injection)
+  http.Client client;
+  SpotifyControllerModel(this._ctx, this.client) {
     // Set inactive state.
     _setInactiveState();
     // Initialise required connections to Spotify app.
@@ -211,7 +214,7 @@ class SpotifyControllerModel with ChangeNotifier {
     TempoSong selectedSong;
     final String uri;
     try {
-      songs = await GetSongBPMModel.getSongs(cadence);
+      songs = await GetSongBPMModel(this.client).getSongs(cadence);
       if (!_isActive) {
         return;
       }

lib/screens/main_screen.dart

@@ -10,6 +10,7 @@ import 'package:provider/provider.dart';
 import 'package:spotify_sdk/models/image_uri.dart';
 import 'package:spotify_sdk/models/player_state.dart';
 import 'package:tuple/tuple.dart';
+import 'package:http/http.dart' as http;
 
 // MainScreen is the screen that the user will see after confirming connection
 // with Spotify.
@@ -47,7 +48,7 @@ class _MainScreenBodyState extends State<_MainScreenBody> {
   @override
   void initState() {
     super.initState();
-    _spotifyModel = SpotifyControllerModel(context);
+    _spotifyModel = SpotifyControllerModel(context, http.Client());
   }
 
   @override

test/spotify_controller_model_test.dart

@@ -0,0 +1,17 @@
+import 'package:catch_my_cadence/models/spotify_controller_model.dart';
+import 'package:catch_my_cadence/screens/main_screen.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_dotenv/flutter_dotenv.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:http/testing.dart';
+
+void main() async {
+  setUp(() async {
+    await dotenv.load(
+        fileName: "assets/secrets.env"); // MainScreen requires secrets
+  });
+
+  group("Main Screen", () {
+    test('', () async {});
+  });
+}