Add spec for "continue shopping" from cart

https://github.com/openfoodfoundation/openfoodnetwork/issues/4771

spec/features/consumer/shopping/cart_spec.rb

@@ -20,6 +20,26 @@ feature "full-page cart", js: true do
       set_order order
     end
 
+    describe "continue shopping" do
+      it "shows a button leading back to the shop" do
+        # Set up a shopfront message to test that we are not going to the
+        # home tab.
+        # PENDING: this passes only without home tab!
+        #distributor.preferred_shopfront_message = "Test driven farming"
+
+        add_product_to_cart order, product_with_fee, quantity: 2
+        visit main_app.cart_path
+
+        expect(page).to have_link "Continue shopping"
+
+        click_link "Continue shopping"
+
+        expect(page).to have_no_link "Continue shopping"
+        expect(page).to have_button "Edit your cart"
+        #expect(page).to have_no_content distributor.preferred_shopfront_message
+      end
+    end
+
     describe "product description" do
       it "does not link to the product page" do
         add_product_to_cart order, product_with_fee, quantity: 2