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attribute difference agent (#1572)

Lloyd Pick 9 years ago
parent
d741bfdc5c
commit
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2 changed files with 242 additions and 0 deletions
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  1. 111 0
      app/models/agents/attribute_difference_agent.rb
  2. 131 0
      spec/models/agents/attribute_difference_agent_spec.rb

+ 111 - 0
app/models/agents/attribute_difference_agent.rb
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+module Agents
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+  class AttributeDifferenceAgent < Agent
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+    cannot_be_scheduled!
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+
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+    description <<-MD
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+      The Attribute Difference Agent receives events and emits a new event with
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+      the difference or change of a specific attribute in comparison to the previous
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+      event received.
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+
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+      `path` specifies the JSON path of the attribute to be used from the event.
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+
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+      `output` specifies the new attribute name that will be created on the original payload
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+      and it will contain the difference or change.
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+
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+      `method` specifies if it should be...
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+
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+      * `percentage_change` eg. Previous value was `160`, new value is `116`. Percentage change is `-27.5`
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+      * `decimal_difference` eg. Previous value was `5.5`, new value is `15.2`. Difference is `9.7`
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+      * `integer_difference` eg. Previous value was `50`, new value is `40`. Difference is `-10`
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+
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+      `decimal_precision` defaults to `3`, but you can override this if you want.
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+
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+      `expected_update_period_in_days` is used to determine if the Agent is working.
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+
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+      The resulting event will be a copy of the received event with the difference
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+      or change added as an extra attribute. If you use the `percentage_change` the
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+      attribute will be formatted as such `{{attribute}}_change`, otherwise it will
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+      be `{{attribute}}_diff`.
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+
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+      All configuration options will be liquid interpolated based on the incoming event.
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+    MD
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+
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+    event_description <<-MD
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+      This will change based on the source event.
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+    MD
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+
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+    def default_options
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+      {
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+        'path' => '.data.rate',
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+        'output' => 'rate_diff',
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+        'method' => 'integer_difference',
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+        'expected_update_period_in_days' => 1
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+      }
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+    end
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+
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+    def validate_options
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+      unless options['path'].present? && options['method'].present? && options['output'].present? && options['expected_update_period_in_days'].present?
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+        errors.add(:base, 'The attribute, method and expected_update_period_in_days fields are all required.')
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+      end
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+    end
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+
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+    def working?
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+      event_created_within?(interpolated['expected_update_period_in_days']) && !recent_error_logs?
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+    end
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+
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+    def receive(incoming_events)
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+      incoming_events.each do |event|
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+        handle(interpolated(event), event)
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+      end
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+    end
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+
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+    private
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+
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+    def handle(opts, event)
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+      opts['decimal_precision'] ||= 3
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+      attribute_value = Utils.value_at(event.payload, opts['path'])
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+      attribute_value = attribute_value.nil? ? 0 : attribute_value
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+      payload = event.payload.deep_dup
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+
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+      if opts['method'] == 'percentage_change'
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+        change = calculate_percentage_change(attribute_value, opts['decimal_precision'])
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+        payload[opts['output']] = change
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+
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+      elsif opts['method'] == 'decimal_difference'
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+        difference = calculate_decimal_difference(attribute_value, opts['decimal_precision'])
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+        payload[opts['output']] = difference
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+
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+      elsif opts['method'] == 'integer_difference'
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+        difference = calculate_integer_difference(attribute_value)
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+        payload[opts['output']] = difference
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+      end
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+
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+      created_event = create_event(payload: payload)
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+      log('Propagating new event', outbound_event: created_event, inbound_event: event)
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+      update_memory(attribute_value)
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+    end
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+
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+    def calculate_integer_difference(new_value)
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+      return 0 if last_value.nil?
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+      (new_value.to_i - last_value.to_i)
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+    end
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+
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+    def calculate_decimal_difference(new_value, dec_pre)
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+      return 0.0 if last_value.nil?
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+      (new_value.to_f - last_value.to_f).round(dec_pre.to_i)
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+    end
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+
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+    def calculate_percentage_change(new_value, dec_pre)
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+      return 0.0 if last_value.nil?
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+      (((new_value.to_f / last_value.to_f) * 100) - 100).round(dec_pre.to_i)
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+    end
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+
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+    def last_value
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+      memory['last_value']
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+    end
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+
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+    def update_memory(new_value)
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+      memory['last_value'] = new_value
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+    end
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+  end
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+end

+ 131 - 0
spec/models/agents/attribute_difference_agent_spec.rb
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+require 'rails_helper'
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+
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+describe Agents::AttributeDifferenceAgent do
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+  def create_event(value=nil)
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+    event = Event.new
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+    event.agent = agents(:jane_weather_agent)
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+    event.payload = {
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+      rate: value
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+    }
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+    event.save!
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+
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+    event
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+  end
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+
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+  before do
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+    @valid_params = {
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+      path: 'rate',
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+      output: 'rate_diff',
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+      method: 'integer_difference',
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+      expected_update_period_in_days: '1'
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+    }
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+
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+    @checker = Agents::AttributeDifferenceAgent.new(name: 'somename', options: @valid_params)
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+    @checker.user = users(:jane)
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+    @checker.save!
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+  end
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+
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+  describe 'validation' do
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+    before do
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+      expect(@checker).to be_valid
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+    end
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+
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+    it 'should validate presence of output' do
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+      @checker.options[:output] = nil
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+      expect(@checker).not_to be_valid
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+    end
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+
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+    it 'should validate presence of path' do
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+      @checker.options[:path] = nil
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+      expect(@checker).not_to be_valid
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+    end
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+
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+    it 'should validate presence of method' do
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+      @checker.options[:method] = nil
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+      expect(@checker).not_to be_valid
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+    end
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+
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+    it 'should validate presence of expected_update_period_in_days' do
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+      @checker.options[:expected_update_period_in_days] = nil
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+      expect(@checker).not_to be_valid
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+    end
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+  end
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+
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+  describe '#working?' do
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+    before :each do
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+      # Need to create an event otherwise event_created_within? returns nil
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+      event = create_event
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+      @checker.receive([event])
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+    end
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+
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+    it 'is when event created within :expected_update_period_in_days' do
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+      @checker.options[:expected_update_period_in_days] = 2
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+      expect(@checker).to be_working
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+    end
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+
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+    it 'isnt when event created outside :expected_update_period_in_days' do
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+      @checker.options[:expected_update_period_in_days] = 2
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+
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+      time_travel_to 2.days.from_now do
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+        expect(@checker).not_to be_working
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+      end
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+    end
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+  end
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+
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+  describe '#receive' do
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+    before :each do
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+      @event = create_event('5.5')
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+    end
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+
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+    it 'creates events when memory is empty' do
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+      expect {
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+        @checker.receive([@event])
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+      }.to change(Event, :count).by(1)
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+      expect(Event.last.payload[:rate_diff]).to eq(0)
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+    end
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+
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+    it 'creates event with extra attribute for integer_difference' do
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+      @checker.receive([@event])
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+      event = create_event('6.5')
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+
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+      expect {
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+        @checker.receive([event])
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+      }.to change(Event, :count).by(1)
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+      expect(Event.last.payload[:rate_diff]).to eq(1)
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+    end
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+
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+    it 'creates event with extra attribute for decimal_difference' do
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+      @checker.options[:method] = 'decimal_difference'
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+      @checker.receive([@event])
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+      event = create_event('6.4')
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+
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+      expect {
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+        @checker.receive([event])
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+      }.to change(Event, :count).by(1)
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+      expect(Event.last.payload[:rate_diff]).to eq(0.9)
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+    end
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+
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+    it 'creates event with extra attribute for percentage_change' do
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+      @checker.options[:method] = 'percentage_change'
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+      @checker.receive([@event])
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+      event = create_event('9')
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+
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+      expect {
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+        @checker.receive([event])
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+      }.to change(Event, :count).by(1)
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+      expect(Event.last.payload[:rate_diff]).to eq(63.636)
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+    end
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+
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+    it 'creates event with extra attribute for percentage_change with the correct rounding' do
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+      @checker.options[:method] = 'percentage_change'
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+      @checker.options[:decimal_precision] = 5
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+      @checker.receive([@event])
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+      event = create_event('9')
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+
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+      expect {
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+        @checker.receive([event])
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+      }.to change(Event, :count).by(1)
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+      expect(Event.last.payload[:rate_diff]).to eq(63.63636)
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+    end
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+  end
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+end