A simple guide for how to write unit tests for smart contracts - Example Function

DutchAuction.sol

/// @dev The first one to provide a bid at the currentAskingPrice is awarded the beneficiary's NFT
  /// @dev If a bidder overbids on the NFT they will win the auction and their overage will be returned
  function processBid() 
    public 
    payable 
    atStage(Stages.AuctionStarted)
    validBid()
    returns (uint)
 {    
    bid = msg.value;
    bidder = msg.sender;
    getCurrentAskingPrice(); 
    if (bid > currentAskingPrice) {
      overage = bid.sub(currentAskingPrice);
      bidder.transfer(overage);
      bid = currentAskingPrice;
      stage = Stages.AuctionEnded;  
      payBeneficiary();
      sendToBidder();
    } else if (bid == currentAskingPrice) {
      stage = Stages.AuctionEnded;  
      payBeneficiary();
      sendToBidder();
    } else {
      revert("Bid is lower than currentAskingPrice");
    }
  }