Add serialize-stdout heartbeat

lib/parallel_tests/cli.rb

@@ -26,8 +26,14 @@ def run(argv)
 
     def execute_in_parallel(items, num_processes, options)
       Tempfile.open 'parallel_tests-lock' do |lock|
+        # CI systems often fail when there is no output for a long time, so simulate some output
+        progress_indicator = Thread.new { while true do sleep ENV.fetch('PARALLEL_TEST_HEARTBEAT_INTERVAL', 60).to_f; print '.' end } if options[:serialize_stdout]
         return Parallel.map(items, :in_threads => num_processes) do |item|
           result = yield(item)
+          if progress_indicator && progress_indicator.alive?
+            progress_indicator.exit
+            puts
+          end
           reprint_output(result, lock.path) if options[:serialize_stdout]
           result
         end

spec/integration_spec.rb

@@ -133,6 +133,13 @@ def test_unicode
     expect(result).not_to match(/TEST2.*TEST1.*TEST2/m)
   end
 
+  it "can show simulated output when serializing stdout" do
+    write 'spec/xxx_spec.rb', 'describe("it"){it("should"){sleep 1; puts "TEST1"}}'
+    result = run_tests "spec", :type => 'rspec', :add => "--serialize-stdout", export: 'PARALLEL_TEST_HEARTBEAT_INTERVAL=0.2'
+
+    expect(result).to match(/\.{5}.*TEST1/m)
+  end
+
   it "can serialize stdout and stderr" do
     write 'spec/xxx_spec.rb', '5.times{describe("it"){it("should"){sleep 0.01; $stderr.puts "errTEST1"; puts "TEST1"}}}'
     write 'spec/xxx2_spec.rb', 'sleep 0.01; 5.times{describe("it"){it("should"){sleep 0.01; $stderr.puts "errTEST2"; puts "TEST2"}}}'