Add first basic unit test to Reports::LineItems

This is quite hard and tedious due to its tight coupling with
Permissions::Order but sets the path to adding more of these and
eventually refactoring this class in the future.

spec/lib/open_food_network/reports/line_items_spec.rb

@@ -0,0 +1,54 @@
+require 'spec_helper'
+require 'open_food_network/reports/line_items'
+
+describe OpenFoodNetwork::Reports::LineItems do
+  subject(:reports_line_items) { described_class.new(order_permissions, params) }
+
+  # This object lets us add some test coverage despite the very deep coupling between the class
+  # under test and the various objects it depends on. Other more common moking strategies where very
+  # hard.
+  class FakeOrderPermissions
+    def initialize(line_item)
+      @relation = Spree::LineItem.where(id: line_item.id)
+    end
+
+    def visible_line_items
+      relation
+    end
+
+    def editable_line_items
+      line_item = FactoryBot.create(:line_item)
+      Spree::LineItem.where(id: line_item.id)
+    end
+
+    private
+
+    attr_reader :relation
+  end
+
+  class FakeRansackResult
+    attr_reader :result
+
+    def initialize(result)
+      @result = result
+    end
+  end
+
+  describe '#list' do
+    let!(:order) { create(:order, distributor: create(:enterprise)) }
+    let!(:line_item) { create(:line_item, order: order) }
+
+    let(:order_permissions) { FakeOrderPermissions.new(line_item) }
+    let(:params) { {} }
+
+    before do
+      orders_relation = Spree::Order.where(id: order.id)
+      allow(reports_line_items).to receive(:search_orders) { FakeRansackResult.new(orders_relation) }
+    end
+
+    it 'returns masked data' do
+      line_items = reports_line_items.list
+      expect(line_items.first.order.email).to eq(I18n.t('admin.reports.hidden'))
+    end
+  end
+end