Solidity ThrowProxy

TestSupplyChain.sol

pragma solidity ^0.5.0;

import "truffle/Assert.sol";
import "truffle/DeployedAddresses.sol";
import "../contracts/SupplyChain.sol";

contract TestSupplyChain {

    uint public initialBalance = 1 ether;
    SupplyChain sc;
    ThrowProxy throwproxy;
    SupplyChainUser seller;
    SupplyChainUser buyer;

    constructor() public payable{}

    function beforeAll() public{
        Assert.equal(address(this).balance, 1 ether, "Contract was not deployed with initial balance of 1 ether");

        sc = SupplyChain(DeployedAddresses.SupplyChain());    
        throwproxy = new ThrowProxy(address(sc)); 

        seller = new SupplyChainUser();
        buyer = (new SupplyChainUser).value(100)();
    }
    
    function testConstructor() public{
        Assert.equal(sc.skuCount(), 0, "SKU count should be initialized to 0.");
        Assert.equal(sc.owner(), msg.sender, "The owner of the contract should be initialized.");
    }
    
    // Use this test to add an item with price 10 wei
    function testAddItem() public {
        string memory name = "The Item";
        uint price = 10 wei;
        uint expectedSKU = 0;
        uint expectedState = 0;
        address expectedSeller = address(seller);
        address expectedBuyer = address(0);

        seller.addItem(sc, name, price);
        
        (string memory _name, uint _sku, uint _price, uint _state, address _seller, address _buyer) = sc.fetchItem(expectedSKU);

        Assert.equal(_name, name, "Name of the item does not match the expected value");
        Assert.equal(_sku, expectedSKU, "The SKU of the item does not match the expected value");
        Assert.equal(_price, price, "The price of the item does not match the expected value");
        Assert.equal(_state, expectedState, "The state of the item does not match the expected value");
        Assert.equal(_seller, expectedSeller, "The seller address of the item does not match the expected value");
        Assert.equal(_buyer, expectedBuyer, "The buyer address of the item does not match the expected value (0)");
    }

    // buyItem

    // test for failure if user does not send enough funds
    // test for purchasing an item that is not for Sale

    function testBuyItemNotEnoughFunds() public {
        string memory expectedName = "The Item";
        uint expectedSKU = 0;
        uint expectedState = 1;
        uint sellerInitBalance = address(seller).balance;
        uint buyerInitBalance = address(buyer).balance;
        
        Assert.equal(sellerInitBalance, 0, "Buyer initial balance should be 0.");
        Assert.equal(buyerInitBalance, 100, "Buyer initial balance should be 100 wei.");
        
        buyer.buyItem(SupplyChain(address(throwproxy)), 0, 1);
        bool r = throwproxy.execute.gas(200000)();
        Assert.isFalse(r, "Should be false because not enough funds were sent!");
    }

    function() external{
    }
}

contract SupplyChainUser {

    constructor() public payable{}
    // Functions for the seller
    function addItem(SupplyChain _supplyChain, string memory _item, uint _price) public returns (bool) {
        
        return _supplyChain.addItem(_item, _price);
    }

    function shipItem(SupplyChain _supplyChain, uint _sku) public {
        
        _supplyChain.shipItem(_sku);
    }

    // Functions for the buyer
    function buyItem(SupplyChain _supplyChain, uint _sku, uint amount) public returns(bool){
         
        _supplyChain.buyItem.value(amount)(_sku);
    }

    function receiveItem(SupplyChain _supplyChain, uint _sku) public {

        _supplyChain.receiveItem(_sku);
    }

    function() external payable{
    }
}

// Proxy contract for testing throws
contract ThrowProxy {
  address public target;
  bytes data;

  constructor(address _target) public {
    target = _target;
  }

  //prime the data using the fallback function.
  function() external{
    data = msg.data;
  }

  function execute() public returns (bool) {
    (bool r, bytes memory b) = target.call(data);
    return(r);
  }
}

Thanks. It helps in understanding the Solidity unit testing

Just a quick thing, when I am running the test case it says 0 passing. Not sure why?