5.1 KiB
Decentralized Finance
I accidentally killed it - devops199
It is time for us to advance beyond basic contracts for integrate with actual DeFi smart contract. For this we will need to use current standards and implementations.
First, we will create a simple stablecoin, following the ERC20 standard and an oracle. We will then create a decentralized exchange that will allow us to exchange our stablecoin. Finally, we will create the tests for this project.
Content
StablecoinLending PlatformTest and Coverage
Integration
-> Audited
Exercise 1: Stablecoin
The purpose of this exercise is to create a fully collateralized stablecoin. We will use an oracle smart contract to get the current value of any volatile token.
Instructions
First, we need a very basic oracle smart contract.
- Create a smart contract
oracle - Add a function getEthPrice() that gives the current value of Ether
- Add a function setEthPrice() that allows the owner of the contract to set the value of Ether
Then, we will create a stablecoin smart contract. It will allow user to mint and burn the stablecoin providing they have the correct amount of collateral.
- Create a
stablecoinsmart contract that inherit from the ERC20 standard - Add a function
registerOraclethat identifies the oracle smart contract - Add a payable function
deposit()that allow the user to deposit Ether to the contract - Add a
withdraw(amount)function that allows any user to receive the corresponding value in Ether providing the user has a sufficient position. - Add a function
mint(amount)that allow the user to mint the stablecoin for up to half the value deposited in Ether - add a
burn(amount)function that allows any user to burn the corresponding value in stablecoin providing the user has a sufficient position.
And, the keystone, we allow any user to punish users that issued more tokens than they should.
- Add a
liquidate(user)function that allows any user to liquidate the position of any user which current position is below this 1:2 ratio. The liquidator must provide the corresponding value in stablecoin and receives 80% of the outstanding deposit in Ether.
Resources
- ERC20 token standard
- For inspiration, MakerDao documentation
Exercise 2: Lending Platform
We will create a platforms that allow borrowers tokens from lenders in a decentralized manner around a volatile and a stable token. Lenders will earn a fixed yield of 5% per year.
Instructions
-
Create or import an implementation of the ERC20 standard mandatory functions with additionally the
name()optional function. (you can add other optional functions). -
Create a script and the documentation to deploy instances of this ERC20 implementation:
VolatileStablelStablelVolatile
-
Expand the
oraclesmart contract from the prior exercise:- Add a function
getPrice()that gives the current value ofVolatileinStable - Add a function
setPrice(uint)that allow to set the value ofVolatileinStable
- Add a function
-
Create a
LendingPlatformsmart contract with :- A constructor that takes in parameters the addresses the tokens mentioned above
- A function
registerOracle(address)that identifies the oracle used - A function
depositStable(amount)that allows a lender to deposit the amount in the Stable token. In exchange, the lender will receive the corresponding amount in lStable. - A function
depositVolatile(amount)that allows an user to deposit the amount in the Volatile . In exchange, the lender will receive the corresponding amount in lVolatile. - A function
borrowStable(amount)that allows a borrower to borrow the amount in the Stable token. It will be required to have more at 150% of its value in volatile token.
-
Add a
liquidate(address)function that allows any user to liquidate the full position of any user which current position is below the 150% threshold. The liquidator needs to provide 110% of the value of the position in the Stable token and will receive the reminder of the value
Optional provide a web interface for the lending platform
Resources
- ERC20 token standard
- For inspiration, AAVE documentation
Exercise 3: Tests and Coverage
To produce adequate tests is the first obvious step to start applying good security measures. We will create the tests for the stablecoin smart contract.
Instructions
- For each function of the
stablecoinsmart contract, create two tests, one that handles the failure of the function and one that handles the success of the function. You can use any testing framework. - Provide the documentation to run your tests. Once a testing framework is available, the user should be able to launch the tests with one command line.