This is solution to below problem statement. It is an attempt for CosmWasm smart contracts - basic course certification.
Tests are implemented using cw-multi-test crate. It implements following test cases:
- Example flow without commision
- Example flow with commission Commission can be either between [0,25]% or round number of atoms (0 or more).
- Owner must not be able bid
- Any bidder (or even owner - which is NA) must not be able to retract on an open bid
Create a smart contract for bidding procedure. The project should be a public git repository created by yourself, send us the repository address.
At instantion, user opens a bid for some offchain commodity. Bid will be happening using only single native token (for eg. atom). Contract owner is optionally provided by its creator - if missing, contract creator is considered its owner.
After contract is instantiated, any user other than the contract owner can raise his bid by sending tokens to the contract with the bid {} message. When the message is called, part of the tokens send are immediately considered bidding commission and should be transferred to contract owner. It is up to you to figure out how to calculate commission.
The total bid of the user is considered to be a sum of all bids performed minus all the commissions. When user raises his bid, it should success only if his total bid is the highest of all other users bids. If it is less or the same as the highest, bidding should fail.
Owner can close {} the bidding at any time. When the bidding is closed, address with the highest total bid is considered the bidding winner. The whole bidding of his is transferred to the contract owner.
After the bidding is closed, everyone who bid and didn't win the bidding, can retract {} all his funds. Additionally the retract message should have an optional friend receiver being an address where the sender biddings should be send. So retract {} sends all senders bids (minus commissions) to his account. The retract { "receiver": "addr" } should send all the sender bids to the "addr" account.
Additionally - all the information kept on the contract should be queryable in reasonable manner. The most important queries are: the given addr total bid, the highest bid at the current time (who and how much), if the bidding is closed, who won the bid (if it is closed).
The contract should contain some tests using multitests framework, but I do not expect any particular coverage - 2-3 main flow tests should be enough.
Pre test state: Owner = 0 atoms, ALEX = 25 atoms & ANN = 25 atoms (No commission)
There is the bidding created at bidding_contract address. alex is sending bid {} message with 15 atoms. The highest bid right now is 15 atoms by alex. Now ann is sending bid {} message with 17 atoms. The highest bid is 17 atoms by ann, and total bid by alex is 15 atoms. Now ann is sending another bid {} message with 2 atoms. Now the highest bid is 19 atoms by ann, and total of alex is 15 atoms. Then alex sends bid {} message with 1 atom - this message fails, as it would leave alex at 16 atoms bid total, which is not the highest right now. He has to send more than 5 atoms. alex sends another bid {} with 5 atoms. It makes the highest bid being 20 atoms by alex, and ann has total of 19 atoms bid. The close {} is send by contract owner - alex wins the bid, 20 atoms are send to bid owner from bidding_contract. ann claims her atoms back calling retract {} message.
Post test state: Owner = 20 atoms, ALEX = 5 atoms, ANN = 25 atoms (As Alex is winner with 20 atoms as highest bid)
Pre test state: Owner = 0 atoms, ALEX = 25 atoms & ANN = 25 atoms (Commision of 1 atom per bid)
There is the bidding created at bidding_contract address with owner's commission of 1 atom. alex is sending bid {} message with 15 atoms. The highest bid right now is 14 atoms by alex and owner having commission of 1 atom. Now ann is sending bid {} message with 17 atoms. The highest bid is 16 atoms by ann, and total bid by alex is 14 atoms and owner's total commission of 2 atoms. The close {} is send by contract owner - ann wins the bid (with her balance as 8 atoms), 16 atoms are send to bid owner from bidding_contract with thus having total balance of 18 atoms (16 + 2 as commission). alex claims his atoms back calling retract {} message, thus getting back 14 atoms totaling his balance to 24 atoms.
Post test state: Owner = 18 atoms (16 + 2), ALEX = 24 atoms, ANN = 8 atoms
cargo wasm
cargo test
cosmwasm-check ./target/wasm32-unknown-unknown/release/bidding_platform.wasm