Testing edge cases for smart contracts

[anurag-p6]

Summary
Written the test cases for smart contracts to check the workflow is proper or not at smart contract side.

Description

1. Created 3 test files acc. to the 3 smart contracts to test the cases
2. 1 file for the integration testing
3. Separated out the testing contracts
4. Performed the testing on my local device forge test
5. Discovered the problem in contract(will fixed in next pr).
6. Documented the implementation part in README.md

Outcome & Benefit

1. Test the contract before deploying on mainnet and facing problem(your few $ will be saved on gas ;-) ).
2. Get to know about new error
3. Production grade setup
4. Modularity for the new contributors to understand it and start working with less hassle

P.S. - docs didn't pushed so here is SC

fixes #20