add test; fix division by zero

Author: navaronbracke

lib/src/objects/barcode.dart

@@ -225,8 +225,9 @@ class Barcode {
   List<Offset> scaleCorners(Size targetSize) {
     // The size and corners are in the same coordinate space,
     // which is the camera input.
-    final double scaleX = targetSize.width / size.width;
-    final double scaleY = targetSize.height / size.height;
+    // If the barcode size is unknown, scale to 0,0.
+    final double scaleX = size.width > 0 ? targetSize.width / size.width : 0;
+    final double scaleY = size.height > 0 ? targetSize.height / size.height : 0;
 
     return [
       for (final Offset offset in corners)

test/barcode_test.dart

@@ -0,0 +1,71 @@
+import 'dart:ui';
+
+import 'package:flutter_test/flutter_test.dart';
+import 'package:mobile_scanner/src/objects/barcode.dart';
+
+void main() {
+  group('scaleCorners', () {
+    test('returns empty list if barcode has no size or corners', () {
+      const Barcode barcode = Barcode();
+
+      expect(barcode.scaleCorners(const Size(100, 100)), isEmpty);
+    });
+
+    test('returns empty list if barcode has no corners', () {
+      const Barcode barcode = Barcode(size: Size(200, 200));
+
+      expect(barcode.scaleCorners(const Size(100, 100)), isEmpty);
+    });
+
+    test('returns zeroed corners if barcode has corners but no size', () {
+      const Barcode barcode = Barcode(
+        corners: [Offset.zero, Offset.zero, Offset.zero, Offset.zero],
+      );
+
+      expect(barcode.scaleCorners(const Size(100, 100)), [
+        Offset.zero,
+        Offset.zero,
+        Offset.zero,
+        Offset.zero,
+      ]);
+    });
+
+    test('returns zeroed corners if target size is empty', () {
+      const Barcode barcode = Barcode(
+        size: Size(200, 200),
+        corners: [
+          Offset(50, 50),
+          Offset(150, 50),
+          Offset(150, 150),
+          Offset(50, 150),
+        ],
+      );
+
+      expect(barcode.scaleCorners(Size.zero), [
+        Offset.zero,
+        Offset.zero,
+        Offset.zero,
+        Offset.zero,
+      ]);
+    });
+
+    test('returns scaled corners', () {
+      const Barcode barcode = Barcode(
+        size: Size(100, 100),
+        corners: [
+          Offset(25, 25),
+          Offset(75, 25),
+          Offset(75, 75),
+          Offset(25, 75),
+        ],
+      );
+
+      expect(barcode.scaleCorners(const Size(200, 200)), const [
+        Offset(50, 50),
+        Offset(150, 50),
+        Offset(150, 150),
+        Offset(50, 150),
+      ]);
+    });
+  });
+}