improve SteadyTimer tests

instead of checking when the callback was actually called,
check for when it was added to the callback queue.

This *should* make the test more reliable.

test/test_roscpp/test/src/timer_callbacks.cpp

@@ -74,18 +74,15 @@ class SteadyTimerHelper
     void callback(const SteadyTimerEvent& e)
     {
       bool first = last_call_.isZero();
-      SteadyTime last_call = last_call_;
-      last_call_ = SteadyTime::now();
-      SteadyTime start = last_call_;
+      last_call_ = e.current_real;
 
       if (!first)
       {
-        double time_error = start.toSec() - expected_next_call_.toSec();
+        double time_error = e.current_real.toSec() - e.current_expected.toSec();
         // Strict check if called early, loose check if called late.
-        // The timed wait could be delayed due to scheduling/resources.
-        if (time_error > 1.0 || time_error < -0.01)
+        if (time_error > 0.2 || time_error < -0.01)
         {
-          ROS_ERROR("Call came at wrong time (%f vs. %f)", expected_next_call_.toSec(), start.toSec());
+          ROS_ERROR("Call came at wrong time (expected: %f, actual %f)", e.current_expected.toSec(), e.current_real.toSec());
           failed_ = true;
         }
       }
@@ -125,30 +122,12 @@ class SteadyTimerHelper
           setPeriod(p, true);
         }
       }
-      else
-      {
-        // If this call was very delayed (beyond the next period), the timer will be
-        // scheduled to call back immediately (next expected is set to the current time)
-        expected_next_call_ = std::max(e.current_expected + expected_period_, start);
-      }
-
-      SteadyTime end = SteadyTime::now();
-      last_duration_ = end - start;
 
       ++total_calls_;
     }
 
     void setPeriod(const WallDuration p, bool reset=false)
     {
-      if(reset)
-      {
-        expected_next_call_ = SteadyTime::now() + p;
-      }
-      else
-      {
-        expected_next_call_ = last_call_ + p;
-      }
-
       timer_.setPeriod(p, reset);
       expected_period_ = p;
     }
@@ -161,9 +140,7 @@ class SteadyTimerHelper
     }
 
     SteadyTime last_call_;
-    SteadyTime expected_next_call_;
     WallDuration expected_period_;
-    WallDuration last_duration_;
 
     bool failed_;