while (buy_amt > 0) {
            //Meanwhile there is amount to buy
            offerId = getBestOffer(buy_gem, pay_gem); //Get the best offer for the token pair
            require(offerId != 0, "offerId == 0");
await rubiconMarket.functions[
            "offer(uint256,address,uint256,address,address,address)"
        ](
            parseUnits("100"),
            testCoin.address,
            parseUnits("110", 6),
            testStableCoin.address,
            ethers.constants.AddressZero,
            ethers.constants.AddressZero,
            { from: owner.address }
        )
it("can take an offer with 0 makerFee", async function () {
                const { rubiconMarket, testCoin, owner } = await loadFixture(
                    deployRubiconProtocolFixture
                )
                const balanceBefore = await testCoin.balanceOf(owner.address)
                // in TEST
                const quantity = parseUnits("14")

                // amount that should be received with fee deducted (only Protocol fee!)
                const quantityAfterFee = await rubiconMarket.calcAmountAfterFee(
                    quantity
                )

                // buying TEST with USDCT
                await rubiconMarket.buy(2, quantity)
                // saving new balance state
                const balanceAfter = await testCoin.balanceOf(owner.address)

                // validating that owner received proper amount with ONLY protocol fee charged
                expect(balanceAfter.sub(balanceBefore)).to.be.equal(
                    quantityAfterFee
                )
            })
