Updated teacher_in_study_group? method to check for common teacher role

app/policies/application_policy.rb

@@ -27,30 +27,23 @@ class ApplicationPolicy
   end
   private :no_one
 
-  def everyone_in_study_group
+  def teacher_in_study_group?
     # !! Order is important !!
     if @record.respond_to? :study_group # e.g. submission
-      study_group = @record.study_group
-      return false if study_group.blank?
-
-      study_groups = [study_group]
+      study_groups = @record.study_group
     elsif @record.respond_to? :user # e.g. exercise
-      # ToDo: Add role to study_group_membership and use for check
-      study_groups = @record.user.study_groups
+      study_groups = @record.author.study_groups.where(study_group_memberships: {role: :teacher})
     elsif @record.respond_to? :users # e.g. study_group
-      study_groups = [@record]
+      study_groups = @record
     elsif @record.respond_to? :study_groups # e.g. user
+      # Access is granted regardless of the `@record`'s role in the study group
       study_groups = @record.study_groups
     else
       return false
     end
 
-    @user.study_groups.any? {|i| study_groups.include?(i) }
-  end
-  private :everyone_in_study_group
-
-  def teacher_in_study_group?
-    teacher? && everyone_in_study_group
+    # Instance variable `study_groups` can be one group or an array of group
+    @user.study_groups.where(study_group_memberships: {role: :teacher}).where(id: study_groups).any?
   end
   private :teacher_in_study_group?
 

spec/policies/exercise_policy_spec.rb

@@ -105,8 +105,32 @@ describe ExercisePolicy do
   end
 
   permissions :show? do
-    it 'not grants access to external users' do
-      expect(policy).not_to permit(build(:external_user), exercise)
+    let(:teacher) { create(:teacher) }
+    let(:exercise_not_public) { build(:dummy, public: false) }
+
+    it 'does not grant access to external users' do
+      expect(policy).not_to permit(build(:external_user), exercise_not_public)
+    end
+
+    context 'when a teacher is not a member in the same study group as the exercise author' do
+      it 'not grants access to the user' do
+        expect(policy).not_to permit(teacher, exercise_not_public)
+      end
+    end
+
+    context "when a teacher is only a member of type 'learner' in the same study group as the exercise author" do
+      it 'not grants access to the user' do
+        exercise_not_public.author.study_groups << teacher.study_groups.first
+        expect(policy).not_to permit(teacher, exercise_not_public)
+      end
+    end
+
+    context 'when a teacher and the exercise author are teaching team members of the same study group' do
+      it 'grants access to the user' do
+        exercise_not_public.author.study_groups << teacher.study_groups.first
+        exercise_not_public.author.study_group_memberships.last.update(role: 'teacher')
+        expect(policy).to permit(teacher, exercise_not_public)
+      end
     end
   end