code: public CallActivityMock onExecutionDo(final String serviceId, final Consumer<DelegateExecution> consumer) {
      flowNodeBuilder = flowNodeBuilder.serviceTask(serviceId)
        .camundaDelegateExpression("${id}".replace("id", serviceId));
  
      registerInstance(serviceId, (JavaDelegate) consumer::accept);
      return this;
    }
docs: On execution, the MockProcess will execute the given consumer with a DelegateExecution.
  
  @param serviceId ... the id of the mock delegate
  @param consumer delegate for service task
  @return self