Item removal

tests.rb

@@ -108,6 +108,41 @@ class TestCheckout < Minitest::Test
     assert_equal (30.00 + 10.50), @checkout.total
   end
 
+  # Item removal
+
+  def test_that_removing_an_item_not_in_the_checkout_removes_nothing
+    @checkout.add(:PICO2)
+    @checkout.remove(:PI5)
+
+    assert_equal [:PICO2], @checkout.items
+  end
+
+  def test_that_items_are_removed_one_by_one
+    4.times do
+      @checkout.add(:ZERO2W)
+    end
+
+    3.times do
+      @checkout.add(:PICO2)
+    end
+
+    assert_equal [:ZERO2W, :ZERO2W, :ZERO2W, :ZERO2W, :PICO2, :PICO2, :PICO2].sort, @checkout.items.sort
+
+    @checkout.remove(:ZERO2W)
+
+    assert_equal [:ZERO2W, :ZERO2W, :ZERO2W, :PICO2, :PICO2, :PICO2].sort, @checkout.items.sort
+
+    @checkout.remove(:PICO2)
+
+    assert_equal [:ZERO2W, :ZERO2W, :ZERO2W, :PICO2, :PICO2].sort, @checkout.items.sort
+
+    2.times do
+      @checkout.remove(:PICO2)
+    end
+
+    assert_equal [:ZERO2W, :ZERO2W, :ZERO2W].sort, @checkout.items.sort
+  end
+
   def test_that_total_is_correctly_recalculated_when_items_are_added
     2.times do
       @checkout.add(:PICO2)
@@ -125,4 +160,16 @@ class TestCheckout < Minitest::Test
 
     assert_equal 40.50, @checkout.total
   end
+
+  def test_that_total_is_correctly_recalculated_when_items_are_removed
+    3.times do
+      @checkout.add(:PICO2) # Bulk discount applies
+    end
+
+    assert_equal 10.50, @checkout.total
+
+    @checkout.remove(:PICO2) # Bulk discount no longer applies
+
+    assert_equal 8.00, @checkout.total
+  end
 end