Map<String, Object> variables1 = new HashMap<String, Object>();
variables1.put("stringVar", "test");
variables1.put("myVar", "test123");
ProcessInstance processInstance1 = runtimeService.startProcessInstanceByKey("oneTaskProcess", variables1);
HistoricVariableInstanceQuery query = historyService.createHistoricVariableInstanceQuery();
query.activityInstanceIdIn(processInstance1.getId());
assertEquals(2, query.list().size());
assertEquals(2, query.count());
Map<String, Object> variables2 = new HashMap<String, Object>();
variables2.put("myVar", "test123");
ProcessInstance processInstance2 = runtimeService.startProcessInstanceByKey("oneTaskProcess", variables2);
query.activityInstanceIdIn(processInstance1.getId(), processInstance2.getId());
assertEquals(3, query.list().size());
assertEquals(3, query.count());
}