Adding in assignment variable substitutions.

Fixes PLAT-907
Fixes PLAT-908

test plan
- Make sure those variables are substituted correctly when in an assignment context.

Change-Id: I56f3ba62dc53d9b8a39c5567588d68554092a842
Reviewed-on: https://gerrit.instructure.com/50275
Tested-by: Jenkins
Reviewed-by: Brad Humphrey <brad@instructure.com>
QA-Review: August Thornton <august@instructure.com>
Product-Review: Brad Humphrey <brad@instructure.com>

lib/lti/variable_expander.rb

@@ -255,6 +255,18 @@ module Lti
                        -> { @assignment.points_possible },
                        ASSIGNMENT_GUARD
 
+    register_expansion 'Canvas.assignment.unlockAt', [],
+                       -> { @assignment.unlock_at },
+                       ASSIGNMENT_GUARD
+
+    register_expansion 'Canvas.assignment.lockAt', [],
+                       -> { @assignment.lock_at },
+                       ASSIGNMENT_GUARD
+
+    register_expansion 'Canvas.assignment.dueAt', [],
+                       -> { @assignment.due_at },
+                       ASSIGNMENT_GUARD
+
     register_expansion 'LtiLink.custom.url', [],
                        -> { @controller.show_lti_tool_settings_url(@tool_setting_link_id) },
                        -> { @tool_setting_link_id }

spec/lib/lti/variable_expander_spec.rb

@@ -24,7 +24,9 @@ module Lti
     let(:account) { Account.new(root_account: root_account) }
     let(:course) { Course.new(account: account) }
     let(:user) { User.new }
+    let(:assignment) { Assignment.new }
     let(:substitution_helper) { stub_everything }
+    let(:right_now) { DateTime.now }
     let(:tool) do
       m = mock('tool')
       m.stubs(:id).returns(1)
@@ -235,6 +237,55 @@ module Lti
         end
       end
 
+      context 'context is a course with an assignment' do
+        subject { described_class.new(root_account, course, controller, current_user: user, assignment: assignment) }
+
+        it 'has substitution for $Canvas.assignment.id' do
+          assignment.stubs(:id).returns(2015)
+          exp_hash = {test: '$Canvas.assignment.id'}
+          subject.expand_variables!(exp_hash)
+          expect(exp_hash[:test]).to eq 2015
+        end
+
+        it 'has substitution for $Canvas.assignment.title' do
+          assignment.title = 'Buy as many ducks as you can'
+          exp_hash = {test: '$Canvas.assignment.title'}
+          subject.expand_variables!(exp_hash)
+          expect(exp_hash[:test]).to eq 'Buy as many ducks as you can'
+        end
+
+        it 'has substitution for $Canvas.assignment.pointsPossible' do
+          assignment.stubs(:points_possible).returns(10)
+          exp_hash = {test: '$Canvas.assignment.pointsPossible'}
+          subject.expand_variables!(exp_hash)
+          expect(exp_hash[:test]).to eq 10
+        end
+
+
+
+        it 'has substitution for $Canvas.assignment.unlockAt' do
+          assignment.stubs(:unlock_at).returns(right_now.to_s)
+          exp_hash = {test: '$Canvas.assignment.unlockAt'}
+          subject.expand_variables!(exp_hash)
+          expect(exp_hash[:test]).to eq right_now.to_s
+        end
+
+        it 'has substitution for $Canvas.assignment.lockAt' do
+          assignment.stubs(:lock_at).returns(right_now.to_s)
+          exp_hash = {test: '$Canvas.assignment.lockAt'}
+          subject.expand_variables!(exp_hash)
+          expect(exp_hash[:test]).to eq right_now.to_s
+        end
+
+        it 'has substitution for $Canvas.assignment.dueAt' do
+          assignment.stubs(:due_at).returns(right_now.to_s)
+          exp_hash = {test: '$Canvas.assignment.dueAt'}
+          subject.expand_variables!(exp_hash)
+          expect(exp_hash[:test]).to eq right_now.to_s
+        end
+
+      end
+
       context 'user is logged in' do
 
         it 'has substitution for $Person.name.full' do