anchor.diff:      return description.addDescriptionOf(value);
     }
   
  -  Description describeMismatch(log, Description mismatchDescription) {
  +  Description describeMismatch(logList, Description mismatchDescription) {
       if (frequency != _Frequency.SOME) {
  -      for (LogEntry entry in log) {
  +      for (LogEntry entry in logList) {
           if (entry.action != action || !value.matches(entry.value)) {
             if (entry.action == Action.RETURN || entry.action == Action.PROXY)
               mismatchDescription.add('returned ');
  
positive.code: 
    const _ResultSetMatcher(this.action, this.value, this.frequency);
  
    bool matches(log) {
      for (LogEntry entry in log) {
        // normalize the action; PROXY is like RETURN.
        Action eaction = entry.action;
        if (eaction == Action.PROXY) {
  
negative.code:     return description.add(' times');
    }
  
    Description describeMismatch(logList, Description mismatchDescription) =>
        mismatchDescription.add('was called ${logList.length} times');
  }
  
  /** [happenedExactly] matches an exact number of calls. */
  