add tests for waiting max of 5 seconds for startup

lib/listen/error.rb

@@ -0,0 +1,7 @@
+# frozen_string_literal: true
+
+module Listen
+  class Error < RuntimeError
+    class NotStarted < Error; end
+  end
+end

lib/listen/event/loop.rb

@@ -5,14 +5,15 @@
 require 'timeout'
 require 'listen/event/processor'
 require 'listen/thread'
+require 'listen/error'
 
 module Listen
   module Event
     class Loop
       include Listen::FSM
 
       class Error < RuntimeError
-        class NotStarted < Error; end
+        NotStarted = ::Listen::Error::NotStarted # for backward compatibility
       end
 
       start_state :pre_start
@@ -40,6 +41,7 @@ def started?
 
       MAX_STARTUP_SECONDS = 5.0
 
+      # @raises Error::NotStarted if background thread hasn't started in MAX_STARTUP_SECONDS
       def start
         # TODO: use a Fiber instead?
         return unless state == :pre_start

spec/lib/listen/event/loop_spec.rb

@@ -45,26 +45,40 @@
   end
 
   describe '#start' do
-    before do
+    it 'is started' do
+      expect(processor).to receive(:loop_for).with(1.234)
       expect(Thread).to receive(:new) do |&block|
         block.call
         thread
       end
-
-      expect(processor).to receive(:loop_for).with(1.234)
-
       subject.start
-    end
-
-    it 'is started' do
       expect(subject).to be_started
     end
 
     context 'when start is called again' do
       it 'returns silently' do
+        expect(processor).to receive(:loop_for).with(1.234)
+        expect(Thread).to receive(:new) do |&block|
+          block.call
+          thread
+        end
+        subject.start
         expect { subject.start }.to_not raise_exception
       end
     end
+
+    context 'when state change to :started takes longer than 5 seconds' do
+      before do
+        expect(Thread).to receive(:new) { thread }
+        expect_any_instance_of(::ConditionVariable).to receive(:wait) { } # return immediately
+      end
+
+      it 'raises Error::NotStarted' do
+        expect do
+          subject.start
+        end.to raise_exception(::Listen::Error::NotStarted, "thread didn't start in 5.0 seconds (in state: :starting)")
+      end
+    end
   end
 
   context 'when set up / started' do