support RSpec matcher allow_event

CHANGELOG.md

@@ -2,7 +2,7 @@
 
 ## unreleased
 
- * add RSpec matcher `have_state` (see [issue #147](https://github.com/aasm/aasm/issues/147) for details)
+ * add RSpec matchers `have_state`, `allow_event` (see [issue #147](https://github.com/aasm/aasm/issues/147) for details)
  * add RSpec matcher `transition_from` (see [issue #178](https://github.com/aasm/aasm/issues/178) for details, thanks to [@thomasstephane](https://github.com/thomasstephane))
 
 ## 4.4.1

README.md

@@ -732,6 +732,8 @@ expect(job).to transition_from(:sleeping).to(:running).on_event(:run)
 expect(job).not_to transition_from(:sleeping).to(:cleaning).on_event(:run)
 expect(job).to have_state(:sleeping)
 expect(job).not_to have_state(:running)
+expect(job).to allow_event :run
+expect(job).to_not allow_event :clean
 
 # classes with multiple state machine
 multiple = SimpleMultipleExample.new
@@ -739,10 +741,14 @@ expect(multiple).to transition_from(:standing).to(:walking).on_event(:walk).on(:
 expect(multiple).to_not transition_from(:standing).to(:running).on_event(:walk).on(:move)
 expect(multiple).to have_state(:standing).on(:move)
 expect(multiple).not_to have_state(:walking).on(:move)
+expect(multiple).to allow_event(:walk).on(:move)
+expect(multiple).to_not allow_event(:hold).on(:move)
 expect(multiple).to transition_from(:sleeping).to(:processing).on_event(:start).on(:work)
 expect(multiple).to_not transition_from(:sleeping).to(:sleeping).on_event(:start).on(:work)
 expect(multiple).to have_state(:sleeping).on(:work)
 expect(multiple).not_to have_state(:processing).on(:work)
+expect(multiple).to allow_event(:start).on(:move)
+expect(multiple).to_not allow_event(:stop).on(:move)
 ```
 
 ## <a id="installation">Installation ##

lib/aasm/rspec/allow_event.rb

@@ -0,0 +1,22 @@
+RSpec::Matchers.define :allow_event do |event|
+  match do |obj|
+    @state_machine_name ||= :default
+    obj.aasm(@state_machine_name).may_fire_event?(event)
+  end
+
+  chain :on do |state_machine_name|
+    @state_machine_name = state_machine_name
+  end
+
+  description do
+    "allow event #{expected} (on :#{@state_machine_name})"
+  end
+
+  failure_message do |obj|
+    "expected that the event :#{expected} would be allowed (on :#{@state_machine_name})"
+  end
+
+  failure_message_when_negated do |obj|
+    "expected that the event :#{expected} would not be allowed (on :#{@state_machine_name})"
+  end
+end

spec/unit/rspec_matcher_spec.rb

@@ -40,4 +40,25 @@ describe 'state machine' do
     end
   end
 
+  describe "allow_event" do
+    it "works for simple state machines" do
+      expect(simple).to allow_event :fill_out
+      expect(simple).to_not allow_event :authorise
+      simple.fill_out
+      expect(simple).to allow_event :authorise
+    end
+
+    it "works for multiple state machines" do
+      expect(multiple).to allow_event(:walk).on(:move)
+      expect(multiple).to_not allow_event(:hold).on(:move)
+      multiple.walk
+      expect(multiple).to allow_event(:hold).on(:move)
+
+      expect(multiple).to allow_event(:start).on(:work)
+      expect(multiple).to_not allow_event(:stop).on(:work)
+      multiple.start
+      expect(multiple).to allow_event(:stop).on(:work)
+    end
+  end
+
 end