TF-3267 Implement HTML attachment preview

core/test/utils/standardize_html_sanitizing_transformers_test.dart

@@ -143,5 +143,35 @@ void main() {
 
       expect(result, equals('<img src="cid:email123">'));
     });
+
+    test(
+      'SHOULD persist nav tag and remove href attribute of A tag '
+      'WHEN href is invalid',
+    () {
+      const inputHtml = '<nav href="javascript:alert(1)"></nav>';
+      final result = transformer.process(inputHtml, htmlEscape);
+
+      expect(result, equals('<nav></nav>'));
+    });
+
+    test(
+      'SHOULD persist main tag and remove href attribute of A tag '
+      'WHEN href is invalid',
+    () {
+      const inputHtml = '<main href="javascript:alert(1)"></main>';
+      final result = transformer.process(inputHtml, htmlEscape);
+
+      expect(result, equals('<main></main>'));
+    });
+
+    test(
+      'SHOULD persist footer tag and remove href attribute of A tag '
+      'WHEN href is invalid',
+    () {
+      const inputHtml = '<footer href="javascript:alert(1)"></footer>';
+      final result = transformer.process(inputHtml, htmlEscape);
+
+      expect(result, equals('<footer></footer>'));
+    });
   });
 }

core/test/utils/string_convert_test.dart

@@ -1,5 +1,6 @@
 import 'dart:convert';
 
+import 'package:core/domain/exceptions/string_exception.dart';
 import 'package:core/utils/string_convert.dart';
 import 'package:flutter_test/flutter_test.dart';
 
@@ -159,4 +160,91 @@ void main() {
       });
     });
   });
+
+  group('string convert test:', () {
+    const testText = 'Hello';
+    test(
+      'should use utf8 decoder '
+      'when isHtml is true',
+    () {
+      // arrange
+      final bytes = utf8.encode(testText);
+
+      // act
+      final result = StringConvert.decodeFromBytes(bytes, charset: null, isHtml: true);
+
+      // assert
+      expect(result, testText);
+    });
+
+    test(
+      'should use utf8 decoder '
+      'when charset contains utf-8',
+    () {
+      // arrange
+      final bytes = utf8.encode(testText);
+
+      // act
+      final result = StringConvert.decodeFromBytes(bytes, charset: 'utf-8');
+
+      // assert
+      expect(result, testText);
+    });
+
+    test(
+      'should use latin1 decoder '
+      'when charset contains latin-1',
+    () {
+      // arrange
+      final bytes = latin1.encode(testText);
+
+      // act
+      final result = StringConvert.decodeFromBytes(bytes, charset: 'latin-1');
+
+      // assert
+      expect(result, testText);
+    });
+
+    test(
+      'should use ascii decoder '
+      'when charset contains ascii',
+    () {
+      // arrange
+      final bytes = ascii.encode(testText);
+
+      // act
+      final result = StringConvert.decodeFromBytes(bytes, charset: 'ascii');
+
+      // assert
+      expect(result, testText);
+    });
+
+    test(
+      'should throw NullCharsetException '
+      'when charset is null',
+    () {
+      // arrange
+      final bytes = utf8.encode(testText);
+
+      // assert
+      expect(
+        () => StringConvert.decodeFromBytes(bytes, charset: null),
+        throwsA(isA<NullCharsetException>()),
+      );
+    });
+
+    test(
+      'should throw UnsupportedCharsetException '
+      'when charset is unsupported',
+    () {
+      // arrange
+      final bytes = utf8.encode(testText);
+
+      // assert
+      expect(
+        () => StringConvert.decodeFromBytes(bytes, charset: 'unsupported'),
+        throwsA(isA<UnsupportedCharsetException>()),
+      );
+    });
+  });
 }