Module: Sequent::Test::CommandHandlerHelpers

Defined in:
lib/sequent/test/command_handler_helpers.rb

Overview

Use in tests

This provides a nice DSL for event based testing of your CommandHandler like

given_events InvoiceCreatedEvent.new(args) when_command PayInvoiceCommand.new(args) then_events InvoicePaidEvent.new(args)

Given events are applied against the Aggregate so need to represent a correct sequence of events.

When a command is executed all generated events are captured and can be retrieved using ‘stored_events` or tested using `then_events`.

The ‘then_events` expects one class, expected event, or RSpec matcher for each generated event, in the same order. Example for Rspec config. When a class is passed, only the type of the generated event is tested. When an expected event is passed only the payload is compared using the `have_same_payload_as` matcher defined by this module (`aggregate_id`, `sequence_number`, and `created_at` are not compared). When an RSpec matcher is passed the actual event is matched against this matcher, so you can use `eq` or `have_attributes` to do more specific matching.

RSpec.configure do |config|

config.include Sequent::Test::CommandHandlerHelpers

end

Then in a spec

describe InvoiceCommandHandler do

before :each do
  Sequent.configuration.event_store = Sequent::Test::CommandHandlerHelpers::FakeEventStore.new
  Sequent.configuration.command_handlers = [] # add your command handlers here
  Sequent.configuration.event_handlers = [] # add you event handlers (eg, workflows) here
end

it "marks an invoice as paid" do
  given_events InvoiceCreatedEvent.new(args)
  when_command PayInvoiceCommand(args)
  then_events InvoicePaidEvent(args)
end

end

Defined Under Namespace

Classes: FakeEventStore

Instance Method Summary collapse

Instance Method Details

#given_events(*events) ⇒ Object 



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# File 'lib/sequent/test/command_handler_helpers.rb', line 165

def given_events(*events)
  Sequent.configuration.event_store.commit_events(
    Sequent::Core::BaseCommand.new,
    to_event_streams(events.flatten(1)),
  )
end

#stored_events ⇒ Object 



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# File 'lib/sequent/test/command_handler_helpers.rb', line 193

def stored_events
  Sequent.configuration.event_store.load_events_since_marked_position(@helpers_events_position_mark)[0]
end

#then_events(*expected_events) ⇒ Object 



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# File 'lib/sequent/test/command_handler_helpers.rb', line 177

def then_events(*expected_events)
  matchers = expected_events.flatten(1).map do |expected|
    if expected.is_a?(Sequent::Core::Event)
      have_same_payload_as(expected)
    else
      expected
    end
  end

  expect(stored_events).to match(matchers)
end

#then_no_events ⇒ Object 



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# File 'lib/sequent/test/command_handler_helpers.rb', line 189

def then_no_events
  then_events
end

#when_command(command) ⇒ Object 



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# File 'lib/sequent/test/command_handler_helpers.rb', line 172

def when_command(command)
  @helpers_events_position_mark = Sequent.configuration.event_store.position_mark
  Sequent.configuration.command_service.execute_commands command
end