fix not synchronising test logic to start of mainLoop()

this was violating thread safety of accessors, since the mainLoopWrapper() was reading initial values at the same time as the test thread was reading the same accessors.

tests/executables_src/testTrigger.cc

@@ -197,6 +197,7 @@ BOOST_AUTO_TEST_CASE_TEMPLATE(testTriggerDevToCS, T, test_types) {
 
   app.initialise();
   app.run();
+  app.testModule.mainLoopStarted.wait(); // make sure the module's mainLoop() is entered
 
   auto myCSVar = pvManagers.first->getProcessArray<T>("/myCSVar");
 
@@ -248,6 +249,7 @@ BOOST_AUTO_TEST_CASE_TEMPLATE(testTriggerByCS, T, test_types) {
 
   app.initialise();
   app.run();
+  app.testModule.mainLoopStarted.wait(); // make sure the module's mainLoop() is entered
 
   auto myCSVar = pvManagers.first->getProcessArray<T>("/myCSVar");
   auto theTrigger = pvManagers.first->getProcessArray<T>("/theTrigger");
@@ -307,6 +309,7 @@ BOOST_AUTO_TEST_CASE_TEMPLATE(testTriggerTransferGroup, T, test_types) {
   app.dev2("/REG3")[app.testModule.theTrigger] >> app.testModule.consumingPush3;
   app.initialise();
   app.run();
+  app.testModule.mainLoopStarted.wait(); // make sure the module's mainLoop() is entered
 
   // initialise values
   app.testModule.consumingPush = 0;