diff --git a/spec/models/spree/calculator_spec.rb b/spec/models/spree/calculator_spec.rb
new file mode 100644
index 0000000000..5caf4dca72
--- /dev/null
+++ b/spec/models/spree/calculator_spec.rb
@@ -0,0 +1,36 @@
+require 'spec_helper'
+
+module Spree
+  describe Calculator do
+    let(:calculator) { Spree::Calculator.new }
+    let!(:enterprise) { create(:enterprise) }
+    let!(:order) { create(:order) }
+    let!(:line_item) { create(:line_item, order: order) }
+    let!(:line_item2) { create(:line_item, order: order) }
+
+    before do
+      order.line_items << line_item
+      order.line_items << line_item2
+    end
+
+    describe "#line_items_for" do
+      it "returns the line item if given a line item" do
+        result = calculator.__send__(:line_items_for, line_item)
+
+        expect(result).to eq [line_item]
+      end
+
+      it "returns line items if given an order" do
+        result = calculator.__send__(:line_items_for, order)
+
+        expect(result).to eq [line_item, line_item2]
+      end
+
+      it "returns the original object if given anything else" do
+        result = calculator.__send__(:line_items_for, enterprise)
+
+        expect(result).to eq [enterprise]
+      end
+    end
+  end
+end