Module: Funes::ProjectionTestHelper

Defined in:
app/helpers/funes/projection_test_helper.rb

Overview

Test helper for testing projections in isolation.

Include this module in your test classes to access helper methods that allow you to test individual projection interpretations without needing to process entire event streams.

Examples:

Include in your test

class InventorySnapshotProjectionTest < ActiveSupport::TestCase
  include Funes::ProjectionTestHelper

  test "receiving items increases quantity on hand" do
    initial_state = InventorySnapshot.new(quantity_on_hand: 10)
    event = Inventory::ItemReceived.new(quantity: 5, unit_cost: 9.99)

    result = interpret_event_based_on(InventorySnapshotProjection, event, initial_state)

    assert_equal 15, result.quantity_on_hand
  end
end

Instance Method Summary collapse

Instance Method Details

#interpret_event_based_on(projection_class, event_instance, previous_state, as_of = Time.current) ⇒ ActiveModel::Model, ActiveRecord::Base

Test a single event interpretation in isolation.

This method extracts and executes a single interpretation block from a projection, allowing you to test how specific events transform state without processing entire event streams.

Examples:

Test a single interpretation

initial_state = OrderSnapshot.new(total: 100)
event = Order::ItemAdded.new(amount: 50)

result = interpret_event_based_on(OrderSnapshotProjection, event, initial_state)

assert_equal 150, result.total

Test with validations

state = InventorySnapshot.new(quantity_on_hand: 5)
event = Inventory::ItemShipped.new(quantity: 10)

result = interpret_event_based_on(InventorySnapshotProjection, event, state)

assert_equal -5, result.quantity_on_hand
refute result.valid?

Parameters:

  • projection_class (Class<Funes::Projection>) —

    The projection class being tested.

  • event_instance (Funes::Event) —

    The event to interpret.

  • previous_state (ActiveModel::Model, ActiveRecord::Base) —

    The state before applying the event.

  • as_of (Time, nil) (defaults to: Time.current) —

    Optional timestamp for temporal logic. Defaults to Time.current.

Returns:

  • (ActiveModel::Model, ActiveRecord::Base) —

    The new state after applying the interpretation.



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# File 'app/helpers/funes/projection_test_helper.rb', line 49

def interpret_event_based_on(projection_class, event_instance, previous_state, as_of = Time.current)
  projection_class.instance_variable_get(:@interpretations)[event_instance.class]
                  .call(previous_state, event_instance, as_of)
end