anchor.diff:  /**
    * The behavior of a method call in the mock library is specified
    * with [Responder]s. A [Responder] has a [value] to throw
  - * or return (depending on whether [isThrow] is true or not, respectively),
  + * or return (depending on the type of [action]),
    * and can either be one-shot, multi-shot, or infinitely repeating,
    * depending on the value of [count (1, greater than 1, or 0 respectively).
    */
  
positive.code:     return description.add(' times');
    }
  
    Description describeMismatch(log, Description mismatchDescription) =>
        mismatchDescription.add('was called ${log.length} times');
  }
  
  /** [happenedExactly] matches an exact number of calls. */
  
negative.code: 
    const _ResultSetMatcher(this.action, this.value, this.frequency);
  
    bool matches(logList) {
      for (LogEntry entry in logList) {
        // normalize the action; PROXY is like RETURN.
        Action eaction = entry.action;
        if (eaction == Action.PROXY) {
  