As of v0.18.1 I can use `test_bitcoin-qt -platform cocoa` to run GUI tests; this opens and closes a regtest GUI a bunch of times.

As of master (6e4f6553913978fcdddba30e0bb6f97edcb12e80) it seems to ignore the `-platform cocoa` and just run the test as with `minimal`.

As seen on macOS 10.14.6. Git bisect blames a2714a5c69f0b0506689af04c3e785f71ee0915d in #16578 `Do not pass in command line arguments to QApplication` (@achow101, @ryanofsky)
{
    QString hash = QString::fromStdString(txid.ToString());
    int rows = model.rowCount({});
    for (int row = 0; row < rows; ++row) {
        QModelIndex index = model.index(row, 0, {});
        if (model.data(index, TransactionTableModel::TxHashRole) == hash) {
            return index;
        }
    }
    return {};
}
void BumpFee(TransactionView& view, const uint256& txid, bool expectDisabled, std::string expectError, bool cancel)