implement isNotEqual

Author: ArturAssisComp

lib/new_api_prototype/core_validators/equality_validators.dart

@@ -2,14 +2,10 @@ import '../../localization/l10n.dart';
 import '../constants.dart';
 
 /// This function returns a validator that checks if the user input is equal (using
-/// the == operator) to either `value`. If the condition is satisfied,
+/// the == operator) to `value`. If the condition is satisfied,
 /// the validator returns null, otherwise, it returns
 /// `FormBuilderLocalizations.current.equalErrorText(userInput.toString())`, if
-/// `equalMsg` is not provided.
-///
-/// # Error
-/// - Throws [AssertionError] if not exactly one of `value` or `dynValue` was
-/// provided.
+/// `isEqualMsg` is not provided.
 Validator<T> isEqual<T extends Object?>(
   T value, {
   String Function(String)? isEqualMsg,
@@ -22,3 +18,21 @@ Validator<T> isEqual<T extends Object?>(
             FormBuilderLocalizations.current.equalErrorText(valueString);
   };
 }
+
+/// This function returns a validator that checks if the user input is not equal (using
+/// the != operator) to `value`. If the condition is satisfied,
+/// the validator returns null, otherwise, it returns
+/// `FormBuilderLocalizations.current.notEqualErrorText(userInput.toString())`, if
+/// `isNotEqualMsg` is not provided.
+Validator<T> isNotEqual<T extends Object?>(
+  T value, {
+  String Function(String)? isNotEqualMsg,
+}) {
+  return (T input) {
+    final String valueString = value.toString();
+    return value != input
+        ? null
+        : isNotEqualMsg?.call(valueString) ??
+            FormBuilderLocalizations.current.notEqualErrorText(valueString);
+  };
+}

test/new_api_testing/core_validators/equality_validators/is_not_equal_validator_test.dart

@@ -0,0 +1,114 @@
+import 'package:flutter_test/flutter_test.dart';
+import 'package:form_builder_validators/form_builder_validators.dart';
+
+class _CustomClass {}
+
+void main() {
+  final _CustomClass myObject = _CustomClass();
+
+  group('Validator: isNoEqual', () {
+    final List<
+        ({
+          String description,
+          bool testFails,
+          Object? referenceValue,
+          Object? userInput
+        })> testCases = <({
+      String description,
+      Object? referenceValue,
+      Object? userInput,
+      bool testFails
+    })>[
+      // Edge cases
+      (
+        description: 'Should pass when the input is not null',
+        referenceValue: null,
+        userInput: 123,
+        testFails: false
+      ),
+      (
+        description: 'Should fail when the value is null',
+        referenceValue: null,
+        userInput: null,
+        testFails: true
+      ),
+      (
+        description: 'Should pass when the input is not the empty string',
+        referenceValue: '',
+        userInput: '\t',
+        testFails: false
+      ),
+      (
+        description: 'Should fail when the value is the empty string',
+        referenceValue: '',
+        userInput: '',
+        testFails: true
+      ),
+      // Domain cases
+      (
+        description: 'Should pass when the input is not the integer 123',
+        referenceValue: 123,
+        userInput: 122,
+        testFails: false
+      ),
+      (
+        description:
+            'Should pass when the input is not the string "Hello, World!"',
+        referenceValue: 'Hello, World!',
+        userInput: 'Hello, World',
+        testFails: false
+      ),
+      (
+        description: 'Should fail when the input is "Hello, World!"',
+        referenceValue: 'Hello, World!',
+        userInput: 'Hello, World!',
+        testFails: true
+      ),
+      (
+        description:
+            'Should pass when the input is not the same as a custom object',
+        referenceValue: myObject,
+        userInput: _CustomClass(),
+        testFails: false
+      ),
+      (
+        description:
+            'Should fail when the input is the same as a custom class object',
+        referenceValue: myObject,
+        userInput: myObject,
+        testFails: true
+      ),
+    ];
+
+    for (final (
+          description: String desc,
+          referenceValue: Object? referenceValue,
+          userInput: Object? userInput,
+          testFails: bool testFails
+        ) in testCases) {
+      test(desc, () {
+        final Validator<Object?> v = isNotEqual(referenceValue);
+
+        expect(
+            v(userInput),
+            testFails
+                ? equals(FormBuilderLocalizations.current
+                    .notEqualErrorText(referenceValue.toString()))
+                : isNull);
+      });
+    }
+
+    test('Should return custom error message', () {
+      const String ref = 'hello';
+      const String customErrorMessage = 'custom error';
+      final Validator<Object> v =
+          isNotEqual(ref, isNotEqualMsg: (_) => customErrorMessage);
+
+      // success
+      expect(v(123), isNull);
+
+      // failure
+      expect(v(ref), customErrorMessage);
+    });
+  });
+}