feature: added unit tests and functionality for login use case

Author: BasakK6

lib/validator.dart

@@ -0,0 +1,30 @@
+class Validator {
+  static String? validateEmail(String email) {
+    if (email.isEmpty) {
+      return "Required field";
+    }
+
+    //check for a valid email with a Regular Expression
+    const String emailRegexPattern =
+        r"^[a-zA-Z0-9.a-zA-Z0-9.!#$%&'*+-/=?^_`{|}~]+@[a-zA-Z0-9\w-]+\.[a-zA-Z]+";
+
+    RegExp regExp = RegExp(emailRegexPattern);
+
+    if (!regExp.hasMatch(email)) {
+      return "Please enter a valid email";
+    }
+    return null;
+  }
+
+  static String? validatePassword(String password) {
+    if (password.isEmpty) {
+      return "Required field";
+    }
+
+    if (password.length < 8) {
+      return "Password should be a minimum of 8 characters";
+    }
+
+    return null;
+  }
+}

test/validator_test.dart

@@ -0,0 +1,72 @@
+import 'package:flutter_test/flutter_test.dart';
+import 'package:test_driven_development/validator.dart';
+
+void main() {
+  group("Validator -", () {
+    test("validate for empty email", () {
+      //ARRANGE
+      String email = '';
+
+      //ACT
+      String? result = Validator.validateEmail(email);
+
+      //ASSERT
+      expect(result, "Required field");
+    });
+
+    test("validate for invalid email", () {
+      //ARRANGE
+      String email = 'sdsdsd';
+
+      //ACT
+      String? result = Validator.validateEmail(email);
+
+      //ASSERT
+      expect(result, "Please enter a valid email");
+    });
+
+    test("validate for valid email", () {
+      //ARRANGE
+      String email = 'dev.basakk6@gmail.com';
+
+      //ACT
+      String? result = Validator.validateEmail(email);
+
+      //ASSERT
+      expect(result, null);
+    });
+
+    test("validate for empty password", () {
+      //ARRANGE
+      String password = '';
+
+      //ACT
+      String? result = Validator.validatePassword(password);
+
+      //ASSERT
+      expect(result, "Required field");
+    });
+
+    test("validate for invalid password", () {
+      //ARRANGE
+      String password = '1234567';
+
+      //ACT
+      String? result = Validator.validatePassword(password);
+
+      //ASSERT
+      expect(result, "Password should be a minimum of 8 characters");
+    });
+
+    test("validate for valid password", () {
+      //ARRANGE
+      String password = '12345678';
+
+      //ACT
+      String? result = Validator.validatePassword(password);
+
+      //ASSERT
+      expect(result, null);
+    });
+  });
+}