ERC20 Token Staking

Inspired by a BowTiedPickle twitter post.

Setup

• Install Foundry.
• To run the all tests, in CL enter:

forge test

• To run a specific test (with stack and setup traces displayed):

forge test --match-test [TEST_NAME_HERE] -vvvvv

Exercise Description

Problem specifications are as follows:

• Owner can fund with an ERC-20 reward token and define a total reward rate.
• Users can stake an ERC-20 staking token at any time.
• Users receive rewards (denominated in reward token) proportional to their staked portion of the pool.
• Users can withdraw at any time.
• Users can claim rewards at any time.

Next steps

As I had to refer to existing staking contracts to make progress on this exercise, my future plans for this exercise involve:

• Summarise what I learnt from the studying the reference contracts (in particular, the Playpen ERC20StakingPool.sol contract).
• Wait a sufficiently long time (approximately a month) before attempting this exercise again with no referencing allowed.

Testing Coverage

• A new reward period can be started when reward tokens have already been deposited to the pool: testNewRewardPeriodRewardTokensAlreadyDeposited
• Owner cannot start a new reward period with no reward tokens in the pool: testNewRewardPeriodRewardTokensAlreadyDeposited
• Staking works as intended: testStake
• Cannot stake zero stake tokens: testStakeZeroAmount
• Withdrawing works as intended: testWithdraw
• Cannot withdraw more than your stake token balance: testWithdrawAmountExceedingBalance
• Withdrawing rewards only works as intended: testGetRewards
• Cannot withdraw reward tokens if they haven't been earned yet: testGetRewardsZeroRewards
• Can exit the pool by withdrawing stake tokens and rewards earned: testExitPoolWithStakeAndRewards

Testing improvements:

• Incorporated fuzz testing for: stake amounts, stake duration, withdrawal amounts.

Acknowledgements

When I found myself feeling stuck, I referred to the following contracts:

• ERC20StakingPool.sol from ZeframLou's Playpen (here).
• Staking Rewards from Solidity By Example (here).