rename Result#event to Result#terminus for consistency.

deprecate `Result#event`.

lib/trailblazer/operation/railway.rb

@@ -10,20 +10,26 @@ def self.pass!     ; Activity::Right end
       def self.fail_fast!; Activity::FastTrack::FailFast end
       def self.pass_fast!; Activity::FastTrack::PassFast end
       # @param options Context
-      # @param end_event The last emitted signal in a circuit is usually the end event.
-      def self.Result(end_event, options, *)
-        Result.new(end_event.kind_of?(End::Success), options, end_event)
+      # @param terminus The last emitted signal in a circuit is the end event/terminus.
+      def self.Result(terminus, options, *)
+        Result.new(terminus.kind_of?(End::Success), options, terminus)
       end
 
-      # The Railway::Result knows about its binary state, the context (data), and the last event in the circuit.
+      # The Railway::Result knows about its binary state, the context (data), and
+      # the reached terminus of the circuit.
       class Result < Result # Operation::Result
-        def initialize(success, data, event)
+        def initialize(success, data, terminus)
           super(success, data)
 
-          @event = event
+          @terminus = terminus
         end
 
-        attr_reader :event
+        def event
+          Activity::Deprecate.warn caller_locations[0], %(Using `Result#event` is deprecated, please use `Result#terminus`)
+          terminus
+        end
+
+        attr_reader :terminus
       end
 
       module End

test/docs/result_test.rb

@@ -0,0 +1,38 @@
+require "test_helper"
+
+module A
+  class DocsResultTest < Minitest::Spec
+    Memo = Class.new
+    module Memo::Operation
+      class Create < Trailblazer::Operation
+        step :validate, Output(:failure) => End(:validation_error)
+        step :save
+        include T.def_steps(:validate, :save)
+      end
+    end
+
+    it "exposes {#terminus}" do
+      result = Memo::Operation::Create.(seq: [])
+      assert_equal result.terminus.to_h.inspect, %({:semantic=>:success})
+
+      result = Memo::Operation::Create.(validate: false, seq: [])
+      assert_equal result.terminus.to_h.inspect, %({:semantic=>:validation_error})
+
+      result = Memo::Operation::Create.(save: false, seq: [])
+      assert_equal result.terminus.to_h.inspect, %({:semantic=>:failure})
+    end
+
+    it "deprecates Result#event" do
+      result = Memo::Operation::Create.(seq: [])
+      terminus = nil
+
+      _, warning = capture_io do
+        terminus = result.event
+      end
+      line_no = __LINE__ - 2
+
+      assert_equal warning, %{[Trailblazer] #{File.realpath(__FILE__)}:#{line_no} Using `Result#event` is deprecated, please use `Result#terminus`\n}
+      assert_equal terminus.to_h.inspect, %({:semantic=>:success})
+    end
+  end
+end