Add BaseValidator and CreateValidator classes

app/validators/base_validator.rb

@@ -0,0 +1,50 @@
+# frozen_string_literal: true
+
+# Base class for all validators.
+# This class provides a simple interface for validating objects using ActiveModel validations.
+#
+# Usage:
+#
+#   class CreateCandidateValidator < BaseValidator
+#     validates :name, presence: true
+#     validates :email, presence: true, email: true
+#   end
+#
+#   candidate = Candidate.new(name: '', email: 'john@example.com')
+#   CreateCandidateValidator.valid?(candidate) # => false
+#   CreateCandidateValidator.validate!(candidate) # => raises BaseValidator::ValidationError
+class BaseValidator < SimpleDelegator
+  class ValidationError < StandardError; end
+
+  include ActiveModel::Validations
+
+  # Checks if the object is valid based on the defined validations.
+  #
+  # @param object [Object] The object to be validated.
+  # @param params [Hash] Additional parameters for validation.
+  # @return [Boolean] Returns true if the object is valid, false otherwise.
+  def self.valid?(object, params = {})
+    new(object, params).valid?
+  end
+
+  # Validates the object and raises a ValidationError if it is not valid.
+  #
+  # @param object [Object] The object to be validated.
+  # @param params [Hash] Additional parameters for validation.
+  def self.validate!(object, params = {})
+    validator = new(object, params)
+    return true if validator.valid?
+
+    raise ValidationError, validator.errors.full_messages.join(', ')
+  end
+
+  # Initializes a new instance of BaseValidator.
+  #
+  # @param object [Object] The object to be validated.
+  # @param params [Hash] Additional parameters for validation.
+  def initialize(object, params = {})
+    super(object)
+    @object = object
+    @params = params
+  end
+end

app/validators/candidates/create_validator.rb

@@ -0,0 +1,16 @@
+# frozen_string_literal: true
+
+module Candidates
+  class CreateValidator < BaseValidator
+    validates :name, presence: true
+    validates :email, presence: true, format: { with: URI::MailTo::EMAIL_REGEXP }
+    validates :birthdate, presence: true
+    validate :past_birtdate
+
+    def past_birtdate
+      return if birthdate.blank?
+
+      errors.add(:birthdate, :future_date) if birthdate > Date.current
+    end
+  end
+end

spec/validators/base_validator_spec.rb

@@ -0,0 +1,51 @@
+# frozen_string_literal: true
+
+class Test
+  class Validator < BaseValidator
+    validates :name, presence: true
+    validate :gmail_email
+
+    def gmail_email
+      return if email.to_s.ends_with?('@gmail.com')
+
+      errors.add(:email, 'must be a Gmail address')
+    end
+  end
+end
+
+RSpec.describe BaseValidator do
+  describe '.valid?' do
+    subject(:valid?) { Test::Validator.valid?(candidate) }
+
+    context 'when the candidate is valid' do
+      let(:candidate) { build(:candidate, email: 'john@gmail.com') }
+
+      it { is_expected.to be true }
+    end
+
+    context 'when the candidate is invalid' do
+      let(:candidate) { build(:candidate, email: 'john@hotmail.com') }
+
+      it { is_expected.to be false }
+    end
+  end
+
+  describe '.validate!' do
+    subject(:validate!) { Test::Validator.validate!(candidate) }
+
+    context 'when the candidate is valid' do
+      let(:candidate) { build(:candidate, email: 'john@gmail.com') }
+
+      it { is_expected.to be true }
+    end
+
+    context 'when the candidate is invalid' do
+      let(:candidate) { build(:candidate, name: '', email: 'john@hotmail.com') }
+
+      it 'raises a ValidationError' do
+        expect { validate! }.to raise_error(BaseValidator::ValidationError,
+                                            "Name can't be blank, Email must be a Gmail address")
+      end
+    end
+  end
+end

spec/validators/candidates/create_validator_spec.rb

@@ -0,0 +1,43 @@
+# frozen_string_literal: true
+
+RSpec.describe Candidates::CreateValidator do
+  describe '.valid?' do
+    subject { described_class.valid?(candidate) }
+
+    let(:candidate) { build(:candidate) }
+
+    context 'when the candidate is valid' do
+      it { is_expected.to be true }
+    end
+
+    context 'when the name is blank' do
+      before { candidate.name = '' }
+
+      it { is_expected.to be false }
+    end
+
+    context 'when the email is blank' do
+      before { candidate.email = '' }
+
+      it { is_expected.to be false }
+    end
+
+    context 'when the email is invalid' do
+      before { candidate.email = 'my.email.at.example.com' }
+
+      it { is_expected.to be false }
+    end
+
+    context 'when the birthdate is blank' do
+      before { candidate.birthdate = nil }
+
+      it { is_expected.to be false }
+    end
+
+    context 'when the birthdate is in the future' do
+      before { candidate.birthdate = 1.day.from_now }
+
+      it { is_expected.to be false }
+    end
+  end
+end