How to automate installation of Windows installer on Appveyor CI?
The installation of Windows application can be automated using AutoHotkey (AHK), similar as Winetricks does this for all common apps which support.

Here is example of AHK script which aims to install mentioned application:

Run, mt5setup.exe
WinWait, MetaTrader 5 Setup
ControlClick, Button1
Sleep 100
ControlClick, Button3
WinWait, MetaTrader 5 Setup, Installation successfully completed
ControlClick, Button4
Process, Wait, terminal.exe
Process, Close, terminal.exe


To integrate it with CI, AHK needs to be installed by downloading ZIP file, uncompressing it and passing the above AHK script. Suggested appveyor.yml file:

install:
- curl -sLo https://www.metatrader5.com/en/download
- curl -sLo http://www.autohotkey.com/download/AutoHotkey104805.zip
- unzip *.zip
before_test:
- dir
test_script:
- AutoHotkey.exe install.ahk
build: off
platform: x86


where install.ahk is the file to contain above AHK script which can be dynamically generated or downloaded from some repository.