PHP ZF2单元测试调度方法非常缓慢

I need to test a big site written in ZF2. There is 443 test and about 10000 assertions. Testing with code coverage takes 6 hours! I think I found the problem: In controller's tests I use a dispatch method from AbstractHttpControllerTestCase. Time of execution of dispatch method is increasing after each test (from fractions of second to tens of seconds).I need to test a big site written in ZF2. There