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)
{
    
    TestChain100Setup test;
    for (int i = 0; i < 5; ++i) {
        test.CreateAndProcessBlock({}, GetScriptForRawPubKey(test.coinbaseKey.GetPubKey()));
    }
    auto chain = interfaces::MakeChain();
    std::shared_ptr<CWallet> wallet = std::make_shared<CWallet>(chain.get(), WalletLocation(), WalletDatabase::CreateMock());
    bool firstRun;
    wallet->LoadWallet(firstRun);
    {
        LOCK(wallet->cs_wallet);
        wallet->SetAddressBook(GetDestinationForKey(test.coinbaseKey.GetPubKey(), wallet->m_default_address_type), "", "receive");
        wallet->AddKeyPubKey(test.coinbaseKey, test.coinbaseKey.GetPubKey());
    }
    {
        auto locked_chain = wallet->chain().lock();