lib/mixins/CallTracker.js
function(index) {
    var calls = this.all();
    var call = calls[index];

    return call ? call.object : null;
  }
function(index) {
    var calls = this.all();
    var call = calls[index];

    return call ? call.object : null;
  }
function ( index ) { var calls = this . all ( ) ; var call = calls [ index ] ; return call ? call . object : null ; }
Get the this that were passed to a specific invocation of this spy.

@name Spy#calls#thisArgFor
@function
@param {Integer} index The 0-based invocation index.
@return {Object}
Get the this that were passed to a specific invocation of this spy .