Hook for scheduling tests in a random order

This may help statistically detect implicit dependencies among unit
tests while running in parallel.

3 files changed, 29 insertions, 3 deletions

diff --git a/Source/CTest/cmCTestTestCommand.cxx b/Source/CTest/cmCTestTestCommand.cxx
index a719b09..23cc20e 100644
--- a/Source/CTest/cmCTestTestCommand.cxx
+++ b/Source/CTest/cmCTestTestCommand.cxx
@@ -24,6 +24,7 @@ cmCTestTestCommand::cmCTestTestCommand()
   this->Arguments[ctt_EXCLUDE_LABEL] = "EXCLUDE_LABEL";
   this->Arguments[ctt_INCLUDE_LABEL] = "INCLUDE_LABEL";
   this->Arguments[ctt_PARALLEL_LEVEL] = "PARALLEL_LEVEL";
+  this->Arguments[ctt_SCHEDULE_RANDOM] = "SCHEDULE_RANDOM";
   this->Arguments[ctt_LAST] = 0;
   this->Last = ctt_LAST;
 }
@@ -91,6 +92,11 @@ cmCTestGenericHandler* cmCTestTestCommand::InitializeHandler()
     handler->SetOption("ParallelLevel",
                        this->Values[ctt_PARALLEL_LEVEL]);
     }
+  if(this->Values[ctt_SCHEDULE_RANDOM])
+    {
+    handler->SetOption("ScheduleRandom",
+                       this->Values[ctt_SCHEDULE_RANDOM]);
+    }
   return handler;
 }
 
diff --git a/Source/CTest/cmCTestTestCommand.h b/Source/CTest/cmCTestTestCommand.h
index 73ce913..12314df 100644
--- a/Source/CTest/cmCTestTestCommand.h
+++ b/Source/CTest/cmCTestTestCommand.h
@@ -61,7 +61,8 @@ public:
       "             [INCLUDE include regex] [RETURN_VALUE res] \n" 
       "             [EXCLUDE_LABEL exclude regex] \n"
       "             [INCLUDE_LABEL label regex] \n"
-      "             [PARALLEL_LEVEL level]) \n"
+      "             [PARALLEL_LEVEL level] \n"
+      "             [SCHEDULE_RANDOM on]) \n"
       "Tests the given build directory and stores results in Test.xml. The "
       "second argument is a variable that will hold value. Optionally, "
       "you can specify the starting test number START, the ending test number "
@@ -70,7 +71,9 @@ public:
       "to not run EXCLUDE. EXCLUDE_LABEL and INCLUDE_LABEL are regular "
       "expression for test to be included or excluded by the test "
       "property LABEL. PARALLEL_LEVEL should be set to a positive number "
-      "representing the number of tests to be run in parallel."
+      "representing the number of tests to be run in parallel. "
+      "SCHEDULE_RANDOM will launch tests in a random order, and is "
+      "typically used to detect implicit test dependencies."
       "\n"
       CTEST_COMMAND_APPEND_OPTION_DOCS;
     }
@@ -92,6 +95,7 @@ protected:
     ctt_EXCLUDE_LABEL,
     ctt_INCLUDE_LABEL,
     ctt_PARALLEL_LEVEL,
+    ctt_SCHEDULE_RANDOM,
     ctt_LAST
   };
 };
diff --git a/Source/CTest/cmCTestTestHandler.cxx b/Source/CTest/cmCTestTestHandler.cxx
index 3572b11..56ddec7 100644
--- a/Source/CTest/cmCTestTestHandler.cxx
+++ b/Source/CTest/cmCTestTestHandler.cxx
@@ -491,11 +491,16 @@ int cmCTestTestHandler::ProcessHandler()
 {
   // Update internal data structure from generic one
   this->SetTestsToRunInformation(this->GetOption("TestsToRunInformation"));
-  this->SetUseUnion(cmSystemTools::IsOn(this->GetOption("UseUnion"))); 
+  this->SetUseUnion(cmSystemTools::IsOn(this->GetOption("UseUnion")));
+  if(cmSystemTools::IsOn(this->GetOption("ScheduleRandom")))
+    {
+    this->CTest->SetScheduleType("Random");
+    }
   if(this->GetOption("ParallelLevel"))
     {
     this->CTest->SetParallelLevel(atoi(this->GetOption("ParallelLevel")));
     }
+
   const char* val;
   val = this->GetOption("LabelRegularExpression");
   if ( val )
@@ -1021,12 +1026,23 @@ void cmCTestTestHandler::ProcessDirectory(std::vector<cmStdString> &passed,
   cmCTestMultiProcessHandler::TestMap tests;
   cmCTestMultiProcessHandler::PropertiesMap properties;
   
+  bool randomSchedule = this->CTest->GetScheduleType() == "Random";
+  if(randomSchedule)
+  {
+    srand((unsigned)time(0));
+  }
+
   for (ListOfTests::iterator it = this->TestList.begin();
        it != this->TestList.end(); ++it)
     { 
     cmCTestTestProperties& p = *it;
     cmCTestMultiProcessHandler::TestSet depends;
 
+    if(randomSchedule)
+      {
+      p.Cost = rand();
+      }
+
     if(p.Depends.size())
       {
       for(std::vector<std::string>::iterator i = p.Depends.begin();