go pandas!

.gitignore

@@ -0,0 +1 @@
+.idea

features/step_definitions/teacher_views_average_class_grade.rb

@@ -0,0 +1,16 @@
+Given /^I have an assignment$/ do
+  @teacher = Teacher.new
+  @student1, @student2 = Student.new, Student.new
+  @assignment1, @assignment2 = Assignment.new, Assignment.new
+end
+
+When /^I'm done grading the assignment$/ do
+  @teacher.submit_assignment(@student1,@assignment1)
+  @teacher.record_grade(@student1,90)
+  @teacher.submit_assignment(@student2,@assignment2)
+  @teacher.record_grade(@student2,70)
+end
+
+Then /^I can see the average class grade$/ do
+  @teacher.average_grade.should == 80
+end

features/teacher_can_view_average_class_grade.feature

@@ -0,0 +1,12 @@
+Feature: Teacher can see average class grade
+
+  As a Teacher
+  I can see the average class grade
+  So that I can see overall class performance
+
+   @wip
+  Scenario: Teacher can see average class grade
+
+     Given I have an assignment
+     When I'm done grading the assignment
+     Then I can see the average class grade

lib/teacher.rb

@@ -16,4 +16,10 @@ def submit_assignment(student, assignment)
   def assignment_for_student(student)
     @assignments[student]
   end
+
+  def average_grade
+    sum = 0
+    @assignments.each { |k, v| sum += v.grade }
+    sum / @assignments.length
+  end
 end

spec/teacher_spec.rb

@@ -1,4 +1,6 @@
 require_relative "../lib/teacher"
+require_relative "../lib/student"
+require_relative "../lib/assignment"
 require "rspec"
 
 describe Teacher do
@@ -19,4 +21,22 @@
       subject.record_grade(student, 95)
     end
   end
+
+  describe 'should get average grade' do
+    it 'should get the average grade' do
+      student1, student2 = stub, stub
+      assignment1, assignment2 = mock, mock
+      subject.submit_assignment(student1, assignment1)
+      subject.submit_assignment(student2, assignment2)
+
+      assignment1.should_receive(:grade=).with(90)
+      assignment2.should_receive(:grade=).with(80)
+      subject.record_grade(student1, 90)
+      subject.record_grade(student2, 80)
+
+      assignment1.should_receive(:grade).and_return(90)
+      assignment2.should_receive(:grade).and_return(80)
+      subject.average_grade.should == 85
+    end
+  end
 end