add fallback for null values

Author: denrase

dart/lib/src/hint.dart

@@ -83,11 +83,14 @@ class Hint {
   // Key/Value Storage
 
   void addAll(Map<String, dynamic> keysAndValues) {
-    _internalStorage.addAll(keysAndValues);
+    final withoutNullValues = keysAndValues.map(
+        (key, value) => MapEntry(key, value ?? "null")
+    );
+    _internalStorage.addAll(withoutNullValues);
   }
 
   void set(String key, dynamic value) {
-    _internalStorage[key] = value;
+    _internalStorage[key] = value ?? "null";
   }
 
   dynamic get(String key) {

dart/test/hint_test.dart

@@ -82,6 +82,23 @@ void main() {
     expect(sut.screenshot, attachment);
     expect(sut.viewHierarchy, attachment);
   });
+
+  test('Hint init with map null fallback', () {
+    final hint = Hint.withMap({'fixture-key': null});
+    expect("null", hint.get("fixture-key"));
+  });
+
+  test('Hint addAll with map null fallback', () {
+    final hint = Hint();
+    hint.addAll({'fixture-key': null});
+    expect("null", hint.get("fixture-key"));
+  });
+
+  test('Hint set with null value fallback', () {
+    final hint = Hint();
+    hint.set("fixture-key", null);
+    expect("null", hint.get("fixture-key"));
+  });
 }
 
 class Fixture {