Add spec for LDAP::Access#allowed?

spec/lib/gitlab/ldap/ldap_access_spec.rb

+require 'spec_helper'
+
+describe Gitlab::LDAP::Access do
+  let(:access) { Gitlab::LDAP::Access.new }
+  let(:user) { create(:user) }
+
+  describe :allowed? do
+    subject { access.allowed?(user) }
+
+    context 'when the user cannot be found' do
+      before { Gitlab::LDAP::Person.stub(find_by_dn: nil) }
+
+      it { should be_false }
+    end
+
+    context 'when the user is found' do
+      before { Gitlab::LDAP::Person.stub(find_by_dn: :ldap_user) }
+
+      context 'and the Active Directory disabled flag is set' do
+        before { Gitlab::LDAP::Person.stub(ad_disabled?: true) }
+
+        it { should be_false }
+      end
+
+      context 'and the Active Directory disabled flag is not set' do
+        before { Gitlab::LDAP::Person.stub(ad_disabled?: false) }
+
+        it { should be_true }
+      end
+    end
+  end
+end