taskService.setVariableLocal(task.getId(), "testVar", "anotherTestValue");
ExecutionEntity taskExecution = (ExecutionEntity) runtimeService.createExecutionQuery().singleResult();
assertNotNull(taskExecution);
HistoricVariableInstanceQuery query = historyService.createHistoricVariableInstanceQuery();
assertEquals(2, query.count());
List<HistoricVariableInstance> result = query.list();
HistoricVariableInstance firstVar = result.get(0);
assertEquals("testVar", firstVar.getVariableName());
assertEquals("testValue", firstVar.getValue());
// the variable is in the process instance scope