Showcasing how to do tests for `elm/file` with selenium

Following with that topic:

@Deimos I managed to do it. The solution is a bit hacky, but works, headless or not.

  1. Hack to make selenium tests works in headless selenium driver. · GitHub
    This gist has the code that keeps a reference to the last 20 created input elements.

  2. in selenium, inject that javascript before the form is created:

    with open("./scripts/hack-file-upload.js", "r") as f:
        patch_for_elm_file =

    time.sleep(1) # Not sure this is needed, but is late.

  1. In seleinum, trigger the file dialog of the elm app.

  2. Afterwards call set_file_image_elm_hack

# Awaiter is a custom class, just use regular wait.

def set_file_image_elm_hack(driver: WebDriver, offset: int, path: str):
    id = str(random.randint(111111111, 999999999))
    driver.execute_script("document.addFileInputToDom(arguments[0], arguments[1])", offset, id)

    file_input = WebDriverWait(driver, 30).until(ec.presence_of_element_located((By.XPATH, "//*[@test-id='" + id + "']")))

    driver.execute_script("document.removeFileInputFromDom(arguments[0])", id)
    if not HEADLESS:
  1. This bash script closes the file dialog:
#!/usr/bin/env bash

# The window name is not the same in firefox. we should handle that if we need it.
win_name="Open File"

# Find window PID
for pid in $(xdotool search --name "$win_name"); do
  error=$(xdotool windowactivate $pid 2>&1)
  if [[ "$error" == "" ]]; then

if [[ "$WIN" == "" ]]; then
  echo "Failed to find file dialog window."
  exit 1

# Switch to the window
xdotool windowactivate $WIN

# Press "Open" button
xdotool key --window $WIN alt+c

Wow, thanks! I was going to resort to ports and stuff. I’ll definitely have to test your way, thanks!

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