assertTrue(debugSampler.getProperty("HeaderManager.headers") instanceof NullProperty);
debugSampler.addTestElement(headerManager);
assertFalse(debugSampler.getProperty("HeaderManager.headers") instanceof NullProperty);
assertEquals(debugSampler.getProperty("HeaderManager.headers").getStringValue() ,"[1stLevelTestHeader\ttestValue1]");
debugSampler.addTestElement(headerManager2);
assertEquals(debugSampler.getProperty("HeaderManager.headers").getStringValue() ,"[1stLevelTestHeader\ttestValue1, 2ndLevelTestHeader\ttestValue2]");
assertEquals(2, ((CollectionProperty)debugSampler.getProperty("HeaderManager.headers")).size());
headerManager.recoverRunningVersion();
headerManager2.recoverRunningVersion();