diff --git a/app/controllers/course_management/curriculums_controller.rb b/app/controllers/course_management/curriculums_controller.rb
index ef79810c2..4553a6c94 100644
--- a/app/controllers/course_management/curriculums_controller.rb
+++ b/app/controllers/course_management/curriculums_controller.rb
@@ -3,7 +3,7 @@
 module CourseManagement
   class CurriculumsController < ApplicationController
     include PagyBackendWithHelpers
-    before_action :set_curriculum, only: %i[show edit update destroy courses]
+    before_action :set_curriculum, only: %i[show edit update destroy openable_courses]
 
     def index
       curriculums = Curriculum.includes(:unit)
@@ -44,9 +44,9 @@ def destroy
       redirect_with(message)
     end
 
-    def courses
-      @courses = @curriculum.courses
-      render json: @courses
+    def openable_courses
+      @curriculum = CurriculumDecorator.new(@curriculum)
+      render json: @curriculum.openable_courses_for_active_term
     end
 
     private
diff --git a/app/decorators/curriculum_decorator.rb b/app/decorators/curriculum_decorator.rb
new file mode 100644
index 000000000..840da3112
--- /dev/null
+++ b/app/decorators/curriculum_decorator.rb
@@ -0,0 +1,16 @@
+# frozen_string_literal: true
+
+class CurriculumDecorator < SimpleDelegator
+  def openable_courses_for_active_term(appends: nil)
+    term = AcademicTerm.active.last.try(:term)
+
+    return [] unless term
+
+    courses = semesters.where(term: term)
+                       .includes(:courses)
+                       .where.not(courses: { id: available_courses.pluck(:course_id) })
+                       .order('courses.name')
+                       .map(&:courses)
+    [*appends, courses].flatten
+  end
+end
diff --git a/app/helpers/link_helper.rb b/app/helpers/link_helper.rb
index 85af1c2b8..6d63f8ce9 100644
--- a/app/helpers/link_helper.rb
+++ b/app/helpers/link_helper.rb
@@ -1,62 +1,79 @@
 # frozen_string_literal: true
 
 module LinkHelper
-  def link_to_back(path = nil, text = t('action_group.back'))
-    link_to(
-      fa_icon('arrow-left', text: text),
-      path,
-      class: 'btn btn-secondary btn-sm'
-    )
-  end
-
-  def link_to_destroy(path = nil, text = t('action_group.destroy'))
-    link_to(
-      fa_icon('trash', text: text),
-      path,
-      method: :delete,
-      data: { confirm: t('are_you_sure') },
-      class: 'btn btn-outline-danger btn-sm'
-    )
-  end
-
-  def link_to_edit(path = nil, text = t('action_group.edit'))
-    link_to(
-      fa_icon('pencil', text: text),
-      path,
-      class: 'btn btn-outline-success btn-sm'
-    )
-  end
+  LINKS = {
+    back: {
+      icon: 'arrow-left',
+      text: I18n.t('action_group.back'),
+      options: {
+        class: 'btn btn-secondary btn-sm'
+      }
+    },
+    destroy: {
+      icon: 'trash',
+      text: I18n.t('action_group.destroy'),
+      options: {
+        class: 'btn btn-outline-danger btn-sm',
+        method: :delete,
+        data: { confirm: I18n.t('are_you_sure') }
+      }
+    },
+    edit: {
+      icon: 'pencil',
+      text: I18n.t('action_group.edit'),
+      options: {
+        class: 'btn btn-outline-success btn-sm'
+      }
+    },
+    new: {
+      icon: 'plus',
+      text: I18n.t('action_group.add'),
+      options: {
+        class: 'btn btn-outline-primary btn-sm',
+        id: 'add-button'
+      }
+    },
+    show: {
+      icon: 'eye',
+      text: I18n.t('action_group.show'),
+      options: {
+        class: 'btn btn-outline-info btn-sm'
+      }
+    },
+    update: {
+      icon: 'pencil-square-o',
+      text: I18n.t('action_group.update'),
+      options: {
+        class: 'btn btn-outline-info btn-sm'
+      }
+    },
+    file: {
+      icon: 'file-word-o',
+      text: I18n.t('action_group.file'),
+      options: {
+        class: 'btn btn-secondary btn-sm'
+      }
+    }
+  }.freeze
 
-  def link_to_new(path = nil, text = t('action_group.add'))
-    link_to(
-      fa_icon('plus', text: text),
-      path,
-      class: 'btn btn-outline-primary btn-sm',
-      id: 'add-button'
-    )
+  LINKS.each do |action, configuration|
+    define_method("link_to_#{action}") do |*args|
+      link_builder(args, configuration)
+    end
   end
 
-  def link_to_show(path = nil, text = t('action_group.show'))
-    link_to(
-      fa_icon('eye', text: text),
-      path,
-      class: 'btn btn-outline-info btn-sm'
-    )
-  end
+  private
 
-  def link_to_update(path = nil, text = t('action_group.update'))
+  def link_builder(args, configuration)
+    text, path = split_args_for_link_to(args)
     link_to(
-      fa_icon('pencil-square-o', text: text),
+      fa_icon(configuration[:icon], text: text || configuration[:text]),
       path,
-      class: 'btn btn-outline-info btn-sm'
+      configuration.fetch(:options, {})
     )
   end
 
-  def link_to_file(path = nil, text = t('action_group.file'))
-    link_to(
-      fa_icon('file-word-o', text: text),
-      path,
-      class: 'btn btn-secondary btn-sm'
-    )
+  def split_args_for_link_to(args)
+    args.length == 1 ? [nil, *args] : args
   end
 end
diff --git a/app/models/academic_term.rb b/app/models/academic_term.rb
index ea90125f4..dc071378a 100644
--- a/app/models/academic_term.rb
+++ b/app/models/academic_term.rb
@@ -3,6 +3,9 @@
 class AcademicTerm < ApplicationRecord
   include EnumForTerm
 
+  # callbacks
+  after_save -> { AcademicTerm.where.not(id: id).update(active: false) }, if: :active?
+
   # relations
   has_many :calendars, dependent: :nullify
   has_many :registration_documents, dependent: :nullify
@@ -12,6 +15,7 @@ class AcademicTerm < ApplicationRecord
   validates :start_of_term, presence: true
   validates :end_of_term, presence: true
   validates :active, inclusion: { in: [true, false] }
+  validates_with AcademicTermValidator
 
   # scopes
   scope :active, -> { where(active: true) }
diff --git a/app/validators/academic_term_validator.rb b/app/validators/academic_term_validator.rb
new file mode 100644
index 000000000..09aab524d
--- /dev/null
+++ b/app/validators/academic_term_validator.rb
@@ -0,0 +1,10 @@
+# frozen_string_literal: true
+
+class AcademicTermValidator < ActiveModel::Validator
+  def validate(record)
+    return if record.active?
+    return if AcademicTerm.where.not(id: record.id).exists?(active: true)
+
+    record.errors[:active] << I18n.t('active_check', scope: %i[validators academic_term])
+  end
+end
diff --git a/app/views/account/addresses/index.html.erb b/app/views/account/addresses/index.html.erb
index 1bd97a7e1..c36a21af6 100644
--- a/app/views/account/addresses/index.html.erb
+++ b/app/views/account/addresses/index.html.erb
@@ -1,6 +1,6 @@
 <div class="alert alert-light">
   <%= link_to_back user_path(@user) %>
-  <%= link_to_new(new_user_address_path(@user), t('.new_address')) unless @user.addresses.informal.present? %>
+  <%= link_to_new(t('.new_address'), new_user_address_path(@user)) unless @user.addresses.informal.present? %>
   <%= link_to (@addresses.formal.present? ? t('.update_from_mernis') :  t('.create_from_mernis') ), save_from_mernis_user_addresses_path, class: "btn btn-outline-primary btn-sm"  %>
 </div>
 
diff --git a/app/views/account/identities/index.html.erb b/app/views/account/identities/index.html.erb
index 5ce0b2d62..5b3edefbc 100644
--- a/app/views/account/identities/index.html.erb
+++ b/app/views/account/identities/index.html.erb
@@ -1,6 +1,6 @@
 <div class="alert alert-light">
   <%= link_to_back user_path(@user) %>
-  <%= link_to_new(new_user_identity_path(@user), t('.new_identity')) unless @user.identities.informal.present? %>
+  <%= link_to_new(t('.new_identity'), new_user_identity_path(@user)) unless @user.identities.informal.present? %>
   <%= link_to (@identities.formal.present? ? t('.update_from_mernis') :  t('.create_from_mernis') ), save_from_mernis_user_identities_path, class: "btn btn-outline-primary btn-sm"  %>
 </div>
 
diff --git a/app/views/admin/cities/show.html.erb b/app/views/admin/cities/show.html.erb
index 42113db6e..13f83c1d7 100644
--- a/app/views/admin/cities/show.html.erb
+++ b/app/views/admin/cities/show.html.erb
@@ -29,7 +29,7 @@
       <div class='card-header'>
         <%= fa_icon 'street-view', text: t('.card_header') %>
         <div class="card-header-actions">
-          <%= link_to_new [:new, :admin, @country, @city, :district], t('.new_district_link') %>
+          <%= link_to_new t('.new_district_link'), [:new, :admin, @country, @city, :district] %>
         </div>
       </div>
       <div class='card-body'>
diff --git a/app/views/admin/countries/show.html.erb b/app/views/admin/countries/show.html.erb
index 9d8a5326c..3c3d7b5ab 100644
--- a/app/views/admin/countries/show.html.erb
+++ b/app/views/admin/countries/show.html.erb
@@ -45,7 +45,7 @@
       <div class='card-header'>
         <%= fa_icon 'street-view', text: t('.card_header') %>
         <div class="card-header-actions">
-          <%= link_to_new [:new, :admin, @country, 'city'], t('.new_city_link') %>
+          <%= link_to_new t('.new_city_link'), [:new, :admin, @country, 'city'] %>
         </div>
       </div>
       <div class='card-body'>
diff --git a/app/views/calendar_management/calendars/index.html.erb b/app/views/calendar_management/calendars/index.html.erb
index c46242193..14252cfd7 100644
--- a/app/views/calendar_management/calendars/index.html.erb
+++ b/app/views/calendar_management/calendars/index.html.erb
@@ -4,7 +4,7 @@
       <div class='card-header'>
         <%= fa_icon 'street-view', text: t('.card_header') %>
         <div class='card-header-actions'>
-          <%= link_to_new [:new, :calendar_management, :calendar], t('.new_calendar_link') %>
+          <%= link_to_new t('.new_calendar_link'), [:new, :calendar_management, :calendar] %>
         </div>
       </div>
       <div class='card-body'>
diff --git a/app/views/committee/agenda_types/index.html.erb b/app/views/committee/agenda_types/index.html.erb
index 645f70abc..45b0f16c5 100644
--- a/app/views/committee/agenda_types/index.html.erb
+++ b/app/views/committee/agenda_types/index.html.erb
@@ -1,5 +1,5 @@
 <div class='alert alert-light'>
-  <%= link_to_new new_agenda_type_path, t('.new_agenda_type_link') %>
+  <%= link_to_new t('.new_agenda_type_link'), new_agenda_type_path %>
 </div>
 
 <div class='row'>
diff --git a/app/views/committee/agendas/index.html.erb b/app/views/committee/agendas/index.html.erb
index e14ab6f94..ec1fbe45b 100644
--- a/app/views/committee/agendas/index.html.erb
+++ b/app/views/committee/agendas/index.html.erb
@@ -1,5 +1,5 @@
 <div class='alert alert-light'>
-  <%= link_to_new new_committee_agenda_path(@committee), t('.new_agenda_link') %>
+  <%= link_to_new t('.new_agenda_link'), new_committee_agenda_path(@committee) %>
   <span class="pull-right">
     <%= link_to(fa_icon('archive', text: t('.meetings')),
                 committee_meetings_path(@committee),
diff --git a/app/views/committee/decisions/show.html.erb b/app/views/committee/decisions/show.html.erb
index 25fb5c3cd..bd50ce0e2 100644
--- a/app/views/committee/decisions/show.html.erb
+++ b/app/views/committee/decisions/show.html.erb
@@ -39,7 +39,7 @@
         </table>
       </div>
       <div class="card-footer">
-        <%= link_to_edit(edit_committee_meeting_agenda_decision_path(@committee, @agenda), t('.update_decision')) %>
+        <%= link_to_edit(t('.update_decision'), edit_committee_meeting_agenda_decision_path(@committee, @agenda)) %>
       </div>
     </div>
   </div>
diff --git a/app/views/committee/meetings/index.html.erb b/app/views/committee/meetings/index.html.erb
index ce8ac4ac6..86f5298cc 100644
--- a/app/views/committee/meetings/index.html.erb
+++ b/app/views/committee/meetings/index.html.erb
@@ -1,5 +1,5 @@
 <div class='alert alert-light'>
-  <%= link_to_new new_committee_meeting_path(@committee), t('.new_committee_meeting_link') %>
+  <%= link_to_new t('.new_committee_meeting_link'), new_committee_meeting_path(@committee) %>
   <span class="pull-right">
     <%= link_to(fa_icon('tasks', text: t('.agendas')), committee_agendas_path(@committee),
                 class: 'btn btn-dark btn-sm') %>
diff --git a/app/views/committee/meetings/show.html.erb b/app/views/committee/meetings/show.html.erb
index 8fdea1c26..7ccb215d1 100644
--- a/app/views/committee/meetings/show.html.erb
+++ b/app/views/committee/meetings/show.html.erb
@@ -56,10 +56,10 @@
               <td><%= agenda.decision.try(:decision_no) %></td>
               <td>
                 <% if agenda.decision.present? %>
-                  <%= link_to_show(committee_meeting_agenda_decision_path(@committee, agenda, agenda.decision), t('.show_decision')) %>
-                  <%= link_to_edit(edit_committee_meeting_agenda_decision_path(@committee, agenda), t('.update_decision')) %>
+                  <%= link_to_show(t('.show_decision'), committee_meeting_agenda_decision_path(@committee, agenda, agenda.decision)) %>
+                  <%= link_to_edit(t('.update_decision'), edit_committee_meeting_agenda_decision_path(@committee, agenda)) %>
                 <% else %>
-                  <%= link_to_new(new_committee_meeting_agenda_decision_path(@committee, agenda), t('.create_decision')) %>
+                  <%= link_to_new(t('.create_decision'), new_committee_meeting_agenda_decision_path(@committee, agenda)) %>
                 <% end %>
               </td>
             </tr>
diff --git a/app/views/course_management/available_courses/_evaluation_types.html.erb b/app/views/course_management/available_courses/_evaluation_types.html.erb
index 4ecbf5dff..53281ebc1 100644
--- a/app/views/course_management/available_courses/_evaluation_types.html.erb
+++ b/app/views/course_management/available_courses/_evaluation_types.html.erb
@@ -3,7 +3,7 @@
     <div class='card-header'>
       <%= fa_icon 'list-alt' %><strong><%= t('.card_header') %></strong>
       <span class='pull-right'>
-        <%= link_to_new(new_available_course_evaluation_type_path(@available_course), t('.create_evaluation_type')) %>
+        <%= link_to_new(t('.create_evaluation_type'), new_available_course_evaluation_type_path(@available_course)) %>
       </span>
     </div>
     <div class='card-body'>
diff --git a/app/views/course_management/available_courses/_form.html.erb b/app/views/course_management/available_courses/_form.html.erb
index 73982b4f5..f5292f1b9 100644
--- a/app/views/course_management/available_courses/_form.html.erb
+++ b/app/views/course_management/available_courses/_form.html.erb
@@ -20,16 +20,26 @@
           <% end %>
           <div class='row mt-3'>
             <div class='form-group col-sm-6'>
-              <%= f.association :unit, collection: Unit.active.coursable.order(:name), label_method: :names_depth_cache %>
+              <%= f.association :unit,
+                                collection: Unit.active.coursable.order(:name),
+                                label_method: :names_depth_cache %>
             </div>
             <div class='form-group col-sm-6'>
-              <%= f.association :curriculum, collection: f.object.unit.present? ? f.object.unit.managed_curriculums : [] %>
+              <%= f.association :curriculum,
+                                collection: [*f.object.unit.try(:managed_curriculums)] %>
             </div>
             <div class='form-group col-sm-6'>
-              <%= f.association :coordinator, collection: f.object.unit.present? ? f.object.unit.subtree_employees : [], label_method: lambda { |c| full_name(c) } %>
+              <%= f.association :coordinator,
+                                collection: [*f.object.unit.try(:subtree_employees)],
+                                label_method: lambda { |c| full_name(c) } %>
             </div>
             <div class='form-group col-sm-6'>
-              <%= f.association :course, collection: f.object.curriculum.present? ? f.object.curriculum.courses : [] %>
+              <% if f.object.curriculum %>
+                <% courses = CurriculumDecorator.new(f.object.curriculum)
+                                                .openable_courses_for_active_term(appends: f.object.course) %>
+              <% end %>
+              <%= f.association :course,
+                                collection: [*courses] %>
             </div>
             <div class='form-group col-sm-12'>
               <%= f.button :submit, class: 'btn btn-outline-success btn-sm' %>
diff --git a/app/views/course_management/available_courses/_groups.html.erb b/app/views/course_management/available_courses/_groups.html.erb
index 4538a65eb..fce2a95e4 100644
--- a/app/views/course_management/available_courses/_groups.html.erb
+++ b/app/views/course_management/available_courses/_groups.html.erb
@@ -3,7 +3,7 @@
     <div class='card-header'>
       <%= fa_icon 'cubes' %><b><%= t('.available_course_groups') %></b>
       <span class='pull-right'>
-        <%= link_to_new(new_available_course_available_course_group_path(@available_course), t('.create_available_course_group')) %>
+        <%= link_to_new(t('.create_available_course_group'), new_available_course_available_course_group_path(@available_course)) %>
       </span>
     </div>
     <div class='card-body'>
diff --git a/app/views/course_management/available_courses/_js.html.erb b/app/views/course_management/available_courses/_js.html.erb
index 6713876d3..72df1546f 100644
--- a/app/views/course_management/available_courses/_js.html.erb
+++ b/app/views/course_management/available_courses/_js.html.erb
@@ -1,7 +1,13 @@
 <script type='text/javascript'>
   $(document).ready(function() {
-    $('#available_course_unit_id, #available_course_course_id').select2();
-    $('#available_course_coordinator_id').select2();
+    elements = [
+      '#available_course_coordinator_id',
+      '#available_course_course_id',
+      '#available_course_curriculum_id',
+      '#available_course_unit_id',
+    ]
+
+    $(elements.join(',')).select2();
 
     var parameters = [
       {
@@ -9,7 +15,6 @@
         target: '#available_course_curriculum_id',
         params: { 'unit_id': '#available_course_unit_id' },
         source: '/units/:unit_id/curriculums/',
-        label_attribute: 'name',
         reset_selectors: '#available_course_curriculum_id, #available_course_course_id',
         placeholder: 'Müfredat Seçiniz'
       },
@@ -17,8 +22,7 @@
         el: '#available_course_curriculum_id',
         target: '#available_course_course_id',
         params: { 'curriculum_id': '#available_course_curriculum_id' },
-        source: '/curriculums/:curriculum_id/courses/',
-        label_attribute: 'name',
+        source: '/curriculums/:curriculum_id/openable_courses',
         reset_selectors: '#available_course_course_id',
         placeholder: 'Ders Seçiniz'
       },
diff --git a/app/views/course_management/available_courses/index.html.erb b/app/views/course_management/available_courses/index.html.erb
index 4cd20fa9b..21394d227 100644
--- a/app/views/course_management/available_courses/index.html.erb
+++ b/app/views/course_management/available_courses/index.html.erb
@@ -6,7 +6,7 @@
       <div class="card-header">
         <%= fa_icon 'align-justify', text: t('.available_courses') %>
         <span class='pull-right'>
-          <%= link_to_new new_available_course_path, t('.add_new_available_course') %>
+          <%= link_to_new t('.add_new_available_course'), new_available_course_path %>
         </span>
       </div>
       <div class="card-body">
diff --git a/app/views/course_management/course_group_types/index.html.erb b/app/views/course_management/course_group_types/index.html.erb
index e4449eb80..a659f4157 100644
--- a/app/views/course_management/course_group_types/index.html.erb
+++ b/app/views/course_management/course_group_types/index.html.erb
@@ -1,5 +1,5 @@
 <div class='alert alert-light'>
-  <%= link_to_new new_course_group_type_path, t('.new_course_group_type_link') %>
+  <%= link_to_new t('.new_course_group_type_link'), new_course_group_type_path %>
 </div>
 
 <div class='row'>
diff --git a/app/views/course_management/course_groups/index.html.erb b/app/views/course_management/course_groups/index.html.erb
index f028dea94..6e24a0f48 100644
--- a/app/views/course_management/course_groups/index.html.erb
+++ b/app/views/course_management/course_groups/index.html.erb
@@ -1,5 +1,5 @@
 <div class='alert alert-light'>
-  <%= link_to_new new_course_group_path, t('.new_course_group_link') %>
+  <%= link_to_new t('.new_course_group_link'), new_course_group_path %>
 </div>
 
 <%= render 'search' %>
diff --git a/app/views/course_management/course_types/index.html.erb b/app/views/course_management/course_types/index.html.erb
index 232458c80..0a8c23ca6 100644
--- a/app/views/course_management/course_types/index.html.erb
+++ b/app/views/course_management/course_types/index.html.erb
@@ -1,5 +1,5 @@
 <div class='alert alert-light'>
-  <%= link_to_new new_course_type_path, t('.new_course_type_link') %>
+  <%= link_to_new t('.new_course_type_link'), new_course_type_path %>
 </div>
 
 <div class='row'>
diff --git a/app/views/course_management/courses/index.html.erb b/app/views/course_management/courses/index.html.erb
index 776fc30fb..c218cfd03 100644
--- a/app/views/course_management/courses/index.html.erb
+++ b/app/views/course_management/courses/index.html.erb
@@ -1,5 +1,5 @@
 <div class="alert alert-light">
-  <%= link_to_new new_course_path, t('.add_new_course') %>
+  <%= link_to_new t('.add_new_course'), new_course_path %>
 </div>
 
 <%= render 'search' %>
@@ -65,4 +65,4 @@
       </div>
     </div>
   </div>
-</div>
\ No newline at end of file
+</div>
diff --git a/app/views/course_management/curriculums/_semesters.html.erb b/app/views/course_management/curriculums/_semesters.html.erb
index 2aef4fb6d..3abcd5a28 100644
--- a/app/views/course_management/curriculums/_semesters.html.erb
+++ b/app/views/course_management/curriculums/_semesters.html.erb
@@ -5,8 +5,8 @@
         <div class="card-header">
           <%= fa_icon 'book' %><strong><%= "#{semester.sequence}. #{t('semester')} (#{enum_t(semester, :term)})" %></strong>
           <div class="float-right">
-            <%= link_to_new new_curriculum_semester_curriculum_course_path(semester), t('.add_course') %>
-            <%= link_to_new new_curriculum_semester_curriculum_course_group_path(semester), t('.add_course_group') %>
+            <%= link_to_new t('.add_course'), new_curriculum_semester_curriculum_course_path(semester) %>
+            <%= link_to_new t('.add_course_group'), new_curriculum_semester_curriculum_course_group_path(semester) %>
           </div>
         </div>
 
diff --git a/app/views/course_management/curriculums/index.html.erb b/app/views/course_management/curriculums/index.html.erb
index 576f74d9c..f27cff908 100644
--- a/app/views/course_management/curriculums/index.html.erb
+++ b/app/views/course_management/curriculums/index.html.erb
@@ -1,5 +1,5 @@
 <div class="alert alert-light">
-  <%= link_to_new new_curriculum_path, t('.add_new_curriculum') %>
+  <%= link_to_new t('.add_new_curriculum'), new_curriculum_path %>
 </div>
 <%= render 'search' %>
 <div class='row'>
@@ -45,4 +45,4 @@
       </div>
     </div>
   </div>
-</div>
\ No newline at end of file
+</div>
diff --git a/app/views/first_registration/registration_documents/index.html.erb b/app/views/first_registration/registration_documents/index.html.erb
index ad17090cd..3c35bf497 100644
--- a/app/views/first_registration/registration_documents/index.html.erb
+++ b/app/views/first_registration/registration_documents/index.html.erb
@@ -4,7 +4,7 @@
       <div class='card-header'>
         <%= fa_icon 'align-justify', text: t('.card_header') %>
         <div class='card-header-actions'>
-          <%= link_to_new [:new, :first_registration, :registration_document], t('.new_registration_document_link') %>
+          <%= link_to_new t('.new_registration_document_link'), [:new, :first_registration, :registration_document] %>
         </div>
       </div>
       <div class='card-body'>
diff --git a/app/views/home/index.html.erb b/app/views/home/index.html.erb
index d2431a4ab..fbbdebd0e 100644
--- a/app/views/home/index.html.erb
+++ b/app/views/home/index.html.erb
@@ -1,3 +1,3 @@
 <%= render 'home/templates/admin' %>
 
-<!-- TODO: user rolüne göre template render et -->
\ No newline at end of file
+<!-- TODO: user rolüne göre template render et -->
diff --git a/app/views/layouts/builders/_index.html.erb b/app/views/layouts/builders/_index.html.erb
index d10785a39..cac403c37 100644
--- a/app/views/layouts/builders/_index.html.erb
+++ b/app/views/layouts/builders/_index.html.erb
@@ -4,9 +4,9 @@
       <div class='card-header'>
         <%= fa_icon 'align-justify', text: card_header %>
         <div class='card-header-actions'>
-          <%= link_to_new([
-            :new, namespace.to_sym, klass],
-            t("#{namespace}.#{klass.pluralize}.index.new_#{klass}_link")
+          <%= link_to_new(
+            t("#{namespace}.#{klass.pluralize}.index.new_#{klass}_link"),
+            [:new, namespace.to_sym, klass]
           ) %>
         </div>
       </div>
diff --git a/app/views/references/academic_terms/index.html.erb b/app/views/references/academic_terms/index.html.erb
index e5f91fb07..a627dffb1 100644
--- a/app/views/references/academic_terms/index.html.erb
+++ b/app/views/references/academic_terms/index.html.erb
@@ -1,5 +1,5 @@
 <div class='alert alert-light'>
-  <%= link_to_new(new_academic_term_path, t('.new_academic_term_link')) %>
+  <%= link_to_new(t('.new_academic_term_link'), new_academic_term_path) %>
 </div>
 
 <div class='row'>
diff --git a/app/views/references/terms/index.html.erb b/app/views/references/terms/index.html.erb
index 6e16a318e..98a3a4b03 100644
--- a/app/views/references/terms/index.html.erb
+++ b/app/views/references/terms/index.html.erb
@@ -1,5 +1,5 @@
 <div class='alert alert-light'>
-  <%= link_to_new new_term_path, t('.new_term_link') %>
+  <%= link_to_new t('.new_term_link'), new_term_path %>
 </div>
 
 <div class='row'>
diff --git a/app/views/units/index.html.erb b/app/views/units/index.html.erb
index fa93b14ea..8dd87e6d8 100644
--- a/app/views/units/index.html.erb
+++ b/app/views/units/index.html.erb
@@ -1,5 +1,5 @@
 <div class='alert alert-light'>
-  <%= link_to_new(new_unit_path, t('.new_unit_link')) %>
+  <%= link_to_new(t('.new_unit_link'), new_unit_path) %>
 </div>
 
 <div class='row'>
diff --git a/app/views/users/_addresses.html.erb b/app/views/users/_addresses.html.erb
index 8c903e720..cf6ef3ab2 100644
--- a/app/views/users/_addresses.html.erb
+++ b/app/views/users/_addresses.html.erb
@@ -2,7 +2,7 @@
   <div class="col-sm-12">
     <div class="card">
       <div class="card-body">
-        <%= link_to_new(new_user_address_path(@user), t('.new_address')) unless @user.addresses.informal.present? %>
+        <%= link_to_new(t('.new_address'), new_user_address_path(@user)) unless @user.addresses.informal.present? %>
         <%= link_to (@user.addresses.formal.present? ? t('.update_from_mernis') : t('.create_from_mernis') ), save_address_from_mernis_user_path, class: "btn btn-outline-primary btn-sm"  %>
       </div>
     </div>
diff --git a/app/views/users/_identities.html.erb b/app/views/users/_identities.html.erb
index b985e0504..611926319 100644
--- a/app/views/users/_identities.html.erb
+++ b/app/views/users/_identities.html.erb
@@ -2,7 +2,7 @@
   <div class="col-sm-12">
     <div class="card">
       <div class="card-body">
-        <%= link_to_new(new_user_identity_path(@user), t('.new_identity')) unless @user.identities.informal.present? %>
+        <%= link_to_new(t('.new_identity'), new_user_identity_path(@user)) unless @user.identities.informal.present? %>
         <%= link_to (@user.identities.formal.present? ? t('.update_from_mernis') : t('.create_from_mernis') ), save_identity_from_mernis_user_path, class: "btn btn-outline-primary btn-sm"  %>
       </div>
     </div>
diff --git a/app/views/users/index.html.erb b/app/views/users/index.html.erb
index 0a438c477..45a8b230a 100644
--- a/app/views/users/index.html.erb
+++ b/app/views/users/index.html.erb
@@ -1,5 +1,5 @@
 <div class='alert alert-light'>
-  <%= link_to_new(new_user_path, t('.new_user_link')) %>
+  <%= link_to_new(t('.new_user_link'), new_user_path) %>
 </div>
 
 <div class='row'>
@@ -48,4 +48,4 @@
       </ul>
     </nav>
   </div>
-</div>
\ No newline at end of file
+</div>
diff --git a/config/locales/defaults/en.yml b/config/locales/defaults/en.yml
index 7e2350fee..1028a69ff 100644
--- a/config/locales/defaults/en.yml
+++ b/config/locales/defaults/en.yml
@@ -28,4 +28,4 @@ en:
   cocoon:
     defaults:
       add: 'Add'
-      remove: 'Remove'
\ No newline at end of file
+      remove: 'Remove'
diff --git a/config/locales/defaults/tr.yml b/config/locales/defaults/tr.yml
index cc62e7028..300bc8360 100644
--- a/config/locales/defaults/tr.yml
+++ b/config/locales/defaults/tr.yml
@@ -28,4 +28,4 @@ tr:
   cocoon:
     defaults:
       add: 'Ekle'
-      remove: 'Sil'
\ No newline at end of file
+      remove: 'Sil'
diff --git a/config/locales/validators/en.yml b/config/locales/validators/en.yml
index 5f9fc1225..0d701d291 100644
--- a/config/locales/validators/en.yml
+++ b/config/locales/validators/en.yml
@@ -1,5 +1,7 @@
 en:
   validators:
+    academic_term:
+      active_check: One of the academic terms must be active.
     address:
       max_formal: You can have up to %{limit} formal addresses maximum.
       max_informal: You can add up to %{limit} addresses maximum.
diff --git a/config/locales/validators/tr.yml b/config/locales/validators/tr.yml
index 9641b9f0c..589d9eb37 100644
--- a/config/locales/validators/tr.yml
+++ b/config/locales/validators/tr.yml
@@ -1,5 +1,7 @@
 tr:
   validators:
+    academic_term:
+      active_check: Akademik dönemlerden birinin aktif olması zorunludur.
     address:
       max_formal: En fazla %{limit} tane ikamet adresi ekleyebilirsiniz.
       max_informal: En fazla %{limit} tane adres ekleyebilirsiniz.
diff --git a/config/routes/course_management.rb b/config/routes/course_management.rb
index 86e0ab382..5d52a2e99 100644
--- a/config/routes/course_management.rb
+++ b/config/routes/course_management.rb
@@ -13,7 +13,7 @@
   resources :course_unit_groups
   resources :curriculums do
     member do
-      get :courses, defaults: { format: :json }
+      get :openable_courses, defaults: { format: :json }
     end
   end
 
diff --git a/test/controllers/course_management/curriculums_controller_test.rb b/test/controllers/course_management/curriculums_controller_test.rb
index 670b7636f..baeabf102 100644
--- a/test/controllers/course_management/curriculums_controller_test.rb
+++ b/test/controllers/course_management/curriculums_controller_test.rb
@@ -77,6 +77,17 @@ class CurriculumsControllerTest < ActionDispatch::IntegrationTest
       assert_equal translate('.destroy.success'), flash[:notice]
     end
 
+    test 'should get openable_course' do
+      @curriculum = CurriculumDecorator.new(@curriculum)
+
+      get openable_courses_curriculum_path(@curriculum)
+
+      assert_response :success
+      assert_equal 'application/json', response.content_type
+      assert_equal @curriculum.openable_courses_for_active_term.count,
+                   JSON.parse(response.body).count
+    end
+
     private
 
     def index_path
diff --git a/test/decorators/curriculum_decorator_test.rb b/test/decorators/curriculum_decorator_test.rb
new file mode 100644
index 000000000..e4e33fa64
--- /dev/null
+++ b/test/decorators/curriculum_decorator_test.rb
@@ -0,0 +1,17 @@
+# frozen_string_literal: true
+
+require 'test_helper'
+
+class CurriculumDecoratorTest < ActiveSupport::TestCase
+  setup do
+    @curriculum = CurriculumDecorator.new(curriculums(:one))
+  end
+
+  test 'openable_courses_for_active_term method' do
+    courses = @curriculum.openable_courses_for_active_term
+
+    assert_not_includes courses, courses(:ati)
+    assert_not_includes courses, courses(:test)
+    assert_includes courses, courses(:ydi)
+  end
+end
diff --git a/test/fixtures/academic_terms.yml b/test/fixtures/academic_terms.yml
index 8f1187665..f8f883096 100644
--- a/test/fixtures/academic_terms.yml
+++ b/test/fixtures/academic_terms.yml
@@ -41,7 +41,7 @@ summer_2018_2019:
   active: false
 
 term_to_delete:
-  year: 2018 - 2019
+  year: 2015 - 2016
   term: summer
   start_of_term: 2019-07-05 08:00:00
   end_of_term: 2019-08-13 17:00:00
diff --git a/test/fixtures/courses.yml b/test/fixtures/courses.yml
index e769681b0..0effaa303 100644
--- a/test/fixtures/courses.yml
+++ b/test/fixtures/courses.yml
@@ -113,4 +113,4 @@ course_to_delete:
   unit: bilgisayar_muhendisligi
   program_type: undergraduate
   language: turkce
-  status: active
\ No newline at end of file
+  status: active
diff --git a/test/fixtures/curriculum_courses.yml b/test/fixtures/curriculum_courses.yml
index 93f4e3a05..345446412 100644
--- a/test/fixtures/curriculum_courses.yml
+++ b/test/fixtures/curriculum_courses.yml
@@ -16,3 +16,9 @@ elective_course:
   curriculum_course_group: one
   ects: 2
   type: elective
+
+ydi:
+  course: ydi
+  curriculum_semester: one
+  ects: 3
+  type: compulsory
diff --git a/test/helpers/link_helper_test.rb b/test/helpers/link_helper_test.rb
index b324279ca..60365cb3b 100644
--- a/test/helpers/link_helper_test.rb
+++ b/test/helpers/link_helper_test.rb
@@ -5,44 +5,44 @@
 class LinkHelperTest < ActionView::TestCase
   include FontAwesome::Rails::IconHelper
 
-  test '#link_to_back' do
+  test 'link_to_back method' do
     link = <<-HTML.squish
       <a class="btn btn-secondary btn-sm" href="#"><i class="fa fa-arrow-left"></i> Back</a>
     HTML
-    assert_equal link_to_back('#', 'Back'), link
+    assert_equal link_to_back('Back', '#'), link
   end
 
-  test '#link_to_destroy' do
+  test 'link_to_destroy method' do
     link = <<-HTML.squish
-      <a data-confirm="#{t('are_you_sure')}"
-         class="btn btn-outline-danger btn-sm"
+      <a class="btn btn-outline-danger btn-sm"
+         data-confirm="#{t('are_you_sure')}"
          rel="nofollow" data-method="delete" href="#"><i class="fa fa-trash"></i> Test Destroy</a>
     HTML
-    assert_equal link_to_destroy('#', 'Test Destroy'), link
+    assert_equal link_to_destroy('Test Destroy', '#'), link
   end
 
-  test '#link_to_edit' do
+  test 'link_to_edit method' do
     link = <<-HTML.squish
       <a class="btn btn-outline-success btn-sm"
          href="#"><i class="fa fa-pencil"></i> Test Edit</a>
     HTML
-    assert_equal link_to_edit('#', 'Test Edit'), link
+    assert_equal link_to_edit('Test Edit', '#'), link
   end
 
-  test '#link_to_new' do
+  test 'link_to_new method' do
     link = <<-HTML.squish
       <a class="btn btn-outline-primary btn-sm" id="add-button"
          href="#"><i class="fa fa-plus"></i> Test New</a>
     HTML
-    assert_equal link_to_new('#', 'Test New'), link
+    assert_equal link_to_new('Test New', '#'), link
   end
 
-  test '#link_to_show' do
+  test 'link_to_show' do
     link = <<-HTML.squish
       <a class="btn btn-outline-info btn-sm"
          href="#"><i class="fa fa-eye"></i> Test Show</a>
     HTML
-    assert_equal link_to_show('#', 'Test Show'), link
+    assert_equal link_to_show('Test Show', '#'), link
   end
 
   test '#link_to_update' do
@@ -50,6 +50,6 @@ class LinkHelperTest < ActionView::TestCase
       <a class="btn btn-outline-info btn-sm"
         href="#"><i class="fa fa-pencil-square-o"></i> Test Update</a>
     HTML
-    assert_equal link_to_update('#', 'Test Update'), link
+    assert_equal link_to_update('Test Update', '#'), link
   end
 end
diff --git a/test/models/academic_term_test.rb b/test/models/academic_term_test.rb
index 0f92c0f8e..027a52a4a 100644
--- a/test/models/academic_term_test.rb
+++ b/test/models/academic_term_test.rb
@@ -41,6 +41,14 @@ class AcademicTermTest < ActiveSupport::TestCase
     assert_not_empty fake_term.errors[:year]
   end
 
+  # validations: AcademicTermValidator
+  test 'one of the academic terms must be active' do
+    active_term = AcademicTerm.active.last
+    active_term.update(active: false)
+    assert_not active_term.valid?
+    assert_not_empty active_term.errors[:active]
+  end
+
   # enums
   test_term_enum(AcademicTerm)
 
@@ -49,4 +57,16 @@ class AcademicTermTest < ActiveSupport::TestCase
     assert_includes AcademicTerm.active, academic_terms(:fall_2018_2019)
     assert_not_includes AcademicTerm.active, academic_terms(:spring_2017_2018)
   end
+
+  # callbacks
+  test 'callbacks only one academic term must be active' do
+    active_term = AcademicTerm.active.last
+    passive_term = academic_terms(:fall_2017_2018)
+
+    passive_term.update!(active: true)
+    active_term.reload
+
+    assert passive_term.active?
+    assert_not active_term.active?
+  end
 end
diff --git a/test/models/curriculum_semester_test.rb b/test/models/curriculum_semester_test.rb
index dcaa8ca6c..3b6e4364e 100644
--- a/test/models/curriculum_semester_test.rb
+++ b/test/models/curriculum_semester_test.rb
@@ -46,6 +46,6 @@ class CurriculumSemesterTest < ActiveSupport::TestCase
 
   # custom methods
   test 'total_ects method' do
-    assert_equal @semester.total_ects, 3.0
+    assert_equal @semester.total_ects, 6.0
   end
 end