Adding tests for KVRow Model

test/models/kvrow_model_test.dart

@@ -0,0 +1,16 @@
+import 'package:test/test.dart';
+import 'package:apidash/models/kvrow_model.dart';
+
+void main() {
+  KVRow kvRow1 = const KVRow("harry", 23);
+  String kvRow1Expected = "{harry: 23}";
+
+  test('Testing toString()', () {
+    expect(kvRow1.toString(), kvRow1Expected);
+  });
+
+  KVRow kvRow2Expected = const KVRow("winter", "26");
+  test('Testing copyWith()', () {
+    expect(kvRow1.copyWith(k: "winter", v: "26"), kvRow2Expected);
+  });
+}