Maybe/test/models/rule/action_test.rb

require "test_helper"

class Rule::ActionTest < ActiveSupport::TestCase
  include Account::EntriesTestHelper

  setup do
    @family = families(:empty)
    @transaction_rule = @family.rules.create!(resource_type: "transaction")
    @account = @family.accounts.create!(name: "Rule test", balance: 1000, currency: "USD", accountable: Depository.new)

    @shopping_category = @family.categories.create!(name: "Shopping")

    # Some sample transactions to work with
    create_transaction(date: Date.current, account: @account, amount: 100, name: "Rule test transaction1", merchant: merchants(:amazon))
    create_transaction(date: Date.current, account: @account, amount: -200, name: "Rule test transaction2")
    create_transaction(date: 1.day.ago.to_date, account: @account, amount: 50, name: "Rule test transaction3")
    create_transaction(date: 1.year.ago.to_date, account: @account, amount: 10, name: "Rule test transaction4", merchant: merchants(:amazon))
    create_transaction(date: 1.year.ago.to_date, account: @account, amount: 1000, name: "Rule test transaction5")

    @rule_scope = @account.transactions
  end

  test "set_transaction_category" do
    action = Rule::Action.new(
      rule: @transaction_rule,
      action_type: "set_transaction_category",
      value: @shopping_category.id
    )

    action.apply(@rule_scope)

    @rule_scope.reload.each do |transaction|
      assert_equal @shopping_category.id, transaction.category_id
    end
  end
end