Is there any way I can get the test cases with which codechef tests my code?!
No, Codechef will only provide you with sample test cases.
But you can also use rand() function to generate your own test case. Since CodeChef provides the necessary constraints, being a programmer you can yourself write a program which generates test cases.
This video might be helpful.
Once you fully understand this, you will find it quite easy to generate test cases.