Add Heya::Campaigns::Step#in_segment?

Exposing this method through Step is useful for unit testing segments
without having to run the scheduler. cc #31

lib/heya/campaigns/scheduler.rb

@@ -30,7 +30,7 @@ def self.process(campaign, step, user)
         ActiveRecord::Base.transaction do
           return if CampaignReceipt.where(user: user, step_gid: step.gid).exists?
 
-          if Heya.in_segments?(user, user.class.__heya_default_segment, campaign.segment, step.segment)
+          if step.in_segment?(user)
             now = Time.now.utc
             Queries::CampaignMembershipsForUpdate.call(campaign, user).update_all(last_sent_at: now)
             CampaignReceipt.create!(user: user, step_gid: step.gid, sent_at: now)

lib/heya/campaigns/step.rb

@@ -13,6 +13,10 @@ def self.find(id)
       def gid
         to_gid(app: "heya").to_s
       end
+
+      def in_segment?(user)
+        Heya.in_segments?(user, user.class.__heya_default_segment, campaign.segment, segment)
+      end
     end
   end
 end

test/lib/heya/campaigns/step_test.rb

@@ -0,0 +1,25 @@
+require "test_helper"
+
+module Heya
+  module Campaigns
+    class StepTest < ActiveSupport::TestCase
+      test "it checks segment for user" do
+        campaign = Class.new(Base) {
+          step :one, segment: ->(c) { c.traits["name"] != "Jack" }
+          user_type "Contact"
+          def self.name
+            "TestCampaign"
+          end
+        }
+        step = campaign.steps.first
+        contact = contacts(:one)
+
+        assert step.in_segment?(contact)
+
+        contact.traits["name"] = "Jack"
+
+        refute step.in_segment?(contact)
+      end
+    end
+  end
+end