Track mock requests.

test/mock-xhr.js

@@ -1,4 +1,5 @@
 function MockXHR() {
+  MockXHR.requests.push(this)
   this.method = null
   this.url = null
   this.data = null
@@ -8,8 +9,13 @@ function MockXHR() {
   this.responseText = null
 }
 
+MockXHR.requests = []
 MockXHR.responses = {}
 
+MockXHR.last = function() {
+  return MockXHR.requests[MockXHR.requests.length - 1]
+}
+
 MockXHR.prototype.open = function(method, url) {
   this.method = method
   this.url = url