1. Swap our ETH for WETH. Token Wrapped Ether(0xd0a1e359811322d97991e03f863a0c30c2cf029c)
2. Deposit some ETH(WETH) into Aave
3. Borrow some asset with the ETH collateral
   1. Sell that borrowed asset. (Short selling)
4. Repay everything back.

Test Default Testing Network: Development with Mocking If you have no oracles: You can use mainnet-fork for testing

Integration test: Kovan
Unit tests: Mainnet-fork (Mock all of mainnet!)