Do not reset global threads

spec/concurrent/executor/timer_set_spec.rb

@@ -10,28 +10,14 @@ module Concurrent
     after(:each){ subject.kill }
 
     context 'construction' do
-
-      before(:all) do
-        reset_gem_configuration
-      end
-
-      after(:each) do
-        reset_gem_configuration
-      end
-
       it 'uses the executor given at construction' do
-        executor = Concurrent.global_immediate_executor
-        expect(executor).to receive(:post).with(no_args)
-        subject = TimerSet.new(executor: executor)
-        subject.post(0){ nil }
+        subject = TimerSet.new(executor: Concurrent.global_immediate_executor)
+        expect(subject.instance_variable_get(:@task_executor)).to eq Concurrent.global_immediate_executor
       end
 
       it 'uses the global io executor be default' do
-        latch = Concurrent::CountDownLatch.new(1)
-        expect(Concurrent.global_io_executor).to receive(:post).with(no_args)
         subject = TimerSet.new
-        subject.post(0){ latch.count_down }
-        latch.wait(0.1)
+        expect(subject.instance_variable_get(:@task_executor)).to eq Concurrent.global_io_executor
       end
     end
 

spec/support/example_group_extensions.rb

@@ -19,22 +19,6 @@ def use_c_extensions?
       Concurrent.allow_c_extensions?
     end
 
-    GLOBAL_EXECUTORS = [
-      [:GLOBAL_FAST_EXECUTOR, -> { Delay.new { Concurrent.new_fast_executor(auto_terminate: true) } }],
-      [:GLOBAL_IO_EXECUTOR, -> { Delay.new { Concurrent.new_io_executor(auto_terminate: true) } }],
-      [:GLOBAL_TIMER_SET, -> { Delay.new { Concurrent::TimerSet.new(auto_terminate: true) } }],
-    ]
-
-    def reset_gem_configuration
-      GLOBAL_EXECUTORS.each do |var, factory|
-        executor = Concurrent.const_get(var).value!
-        executor.shutdown
-        executor.wait_for_termination(0.2)
-        executor.kill
-        Concurrent.const_set(var, factory.call)
-      end
-    end
-
     def monotonic_interval
       raise ArgumentError.new('no block given') unless block_given?
       start_time = GLOBAL_MONOTONIC_CLOCK.get_time