add DetectionSpeed test

@@ -27,7 +27,7 @@ enum DetectionSpeed {
       case 2:
         return DetectionSpeed.unrestricted;
       default:
-        return DetectionSpeed.normal;
+        throw ArgumentError.value(value, 'value', 'Invalid raw value.');
     }
   }
 

+import 'package:flutter_test/flutter_test.dart';
+import 'package:mobile_scanner/src/enums/detection_speed.dart';
+
+void main() {
+  group('$DetectionSpeed tests', () {
+    test('can be created from raw value', () {
+      const values = <int, DetectionSpeed>{
+        0: DetectionSpeed.noDuplicates,
+        1: DetectionSpeed.normal,
+        2: DetectionSpeed.unrestricted,
+      };
+
+      for (final MapEntry<int, DetectionSpeed> entry in values.entries) {
+        final DetectionSpeed result = DetectionSpeed.fromRawValue(entry.key);
+
+        expect(result, entry.value);
+      }
+    });
+
+    test('invalid raw value throws argument error', () {
+      const int negative = -1;
+      const int outOfRange = 3;
+
+      expect(() => DetectionSpeed.fromRawValue(negative), throwsArgumentError);
+      expect(() => DetectionSpeed.fromRawValue(outOfRange), throwsArgumentError);
+    });
+
+    test('can be converted to raw value', () {
+      const values = <DetectionSpeed, int>{
+        DetectionSpeed.noDuplicates: 0,
+        DetectionSpeed.normal: 1,
+        DetectionSpeed.unrestricted: 2,
+      };
+
+      for (final MapEntry<DetectionSpeed, int> entry in values.entries) {
+        final int result = entry.key.rawValue;
+
+        expect(result, entry.value);
+      }
+    });
+  });
+}