runs_sales_report_test.rb

require "date"
require "mocktail"
require "minitest/autorun"

class FetchesOrdersAndItems
  Result = Struct.new(:orders, :items, keyword_init: true)

  def fetch(start_date, end_date)
  end
end

class SummarizesSalesPerformance
  def summarize(orders:, items:)
  end
end

class BuildsReportRows
  def build(summary)
  end
end

class RendersReport
  def render(rows)
  end
end

class RunsSalesReport
  def initialize
    @fetches_orders_and_items = FetchesOrdersAndItems.new
    @summarizes_sales_performance = SummarizesSalesPerformance.new
    @builds_report_rows = BuildsReportRows.new
    @renders_report = RendersReport.new
  end

  def run(start_date, end_date)
    orders_and_items = @fetches_orders_and_items.fetch(start_date, end_date)
    summary = @summarizes_sales_performance.summarize(
      orders: orders_and_items.orders,
      items: orders_and_items.items,
    )
    rows = @builds_report_rows.build(summary)
    @renders_report.render(rows)
  end
end

class RunsSalesReportTest < Minitest::Test
  include Mocktail::DSL

  def setup
    @fetches_orders_and_items = Mocktail.of_next(FetchesOrdersAndItems)
    @summarizes_sales_performance = Mocktail.of_next(SummarizesSalesPerformance)
    @builds_report_rows = Mocktail.of_next(BuildsReportRows)
    @renders_report = Mocktail.of_next(RendersReport)

    @subject = RunsSalesReport.new
  end

  def test_sales_report_summary
    stubs { @fetches_orders_and_items.fetch(Date.civil(2020,1,1), Date.civil(2020,1,31)) }.with {
      FetchesOrdersAndItems::Result.new(orders: [:an_order], items: [:an_item])
    }
    stubs { @summarizes_sales_performance.summarize(orders: [:an_order], items: [:an_item]) }.with { :some_summary }
    stubs { @builds_report_rows.build(:some_summary) }.with { [:a_row] }

    @subject.run(Date.civil(2020,1,1), Date.civil(2020,1,31))

    verify { @renders_report.render([:a_row]) }
  end
end