Is there some way to validate the messages added by my Validators when testing my web flows? I can't figure out how to access the messages.

I'm having good luck testing my flows by creating JUnit classes derived from AbstractXmlFlowExecutionTests. I can successfully populate fields in my model object, resume the flow, and confirm the transitions fire as expected. But I can't figure out how to access the Messages added by the Validators.

(please excuse my pseudo-code)
Specifically, let's say I have a model object and separate validator
Code:
public class Criteria {
  private long value;
  public long getValue() { return value; }
  public void setValue(long argValue) { value = argValue };
}

public class CriteriaValidator {
  public void validateSearchUsingValue(Criteria argCriteria, ValidationContext argContext) {
    if (argCriteria.getValue() < 0) {
        MessageBuilder msgBuilder = new MessageBuilder().error();
        msgBuilder.source("value");
        msgBuilder.code("cocode.domain.cannotBeNegative");
        msgBuilder.args(new Object[] { argCriteria.getValue() });

        argContext.getMessageContext().addMessage(msgBuilder.build());
  }
}
In my test method, after I resume my flow, I successfully assertCurrentStateEquals(). But then I'd like to confirm that the proper message was added. How can I access that message associated with my "value" field?

Thanks in advance.