Headless mode

[byronz]

this solves #793

• the headless mode option is added so you can do pytest --headless True, default is False
• it might be useful for advanced testers to further configure the selenium options via a hook. the current solution opens the options object, I feel it's a good compromise here. But it might be good to know if users wanna full control on the webdriver construction.

Contributor Checklist

• I have broken down my PR scope into the following TODO tasks
  • add headless mode
  • add hooks to configure webdriver options
• I have run the tests locally and they passed. (refer to testing section in contributing)

optionals

• I have added entry in the CHANGELOG.md
• If this PR needs a follow-up in dash docs, community thread, I have mentioned the relevant URLS as follow
  • this github #PR number updates the dash docs

[byronz]

@mmartinsky feel free to add comments on the proposed solution for headless mode.

@alexcjohnson we can probably switch all integration with headless mode too, it's faster. I will test more

[Marc-Andre-Rivet]

💃

[mmartinsky]

Thanks @byronz ! Looking forward to release - do you happen to have any idea on release cadence post 1.0.0?

[alexcjohnson]

Looks like we lost --no-sandbox, is it important?

[byronz]

no, I removed this part as the options are fully configurable after this PR

[alexcjohnson]

could we use "store_true" so you can simplify to pytest --headless, rather than pytest --headless True?

[byronz]

yep, I like the shorter version

[byronz]

Thanks @byronz ! Looking forward to release - do you happen to have any idea on release cadence post 1.0.0?

@mmartinsky we have some internal discussion right now, nothing official yet, but 2-6 weeks, might be less frequent than last few months.

[mmartinsky]

hey @byronz and @alexcjohnson, do you have an example of altering the options for the webdriver? For background, I'm running into DevToolsActivePort file doesn't exist. when running in headless on Gitlab CI.

I found heroku/heroku-buildpack-google-chrome#46 (comment) that seems to be the same issue, I'm hoping that adding these options will clear this up.

The command I'm running is pytest --headless, nothing fancy there. The tests pass locally, but I can't seem to find a way to hook into the Chrome options.

I added a conftest.py at the project root, but it does not seem to get called:

def pytest_setup_options():
    print("Calling hook!!!!")

Output:

(venv) <Machine>:dash-app-kickstart <User>$ pytest --headless -v
Test session starts (platform: darwin, Python 3.7.3, pytest 4.6.3, pytest-sugar 0.9.2)
cachedir: .pytest_cache
rootdir: /some-path/dash-app-kickstart
plugins: sugar-0.9.2, dash-1.0.2, cov-2.7.1, mock-1.10.4
collecting ... 
 tests/test_integration.py::TestClass.test_style_app_title_capitalized ✓                                                                                                                                                                                   25% ██▌       
 tests/test_integration.py::TestClass.test_number_of_tabs ✓                                                                                                                                                                                                50% █████     
 tests/test_integration.py::TestClass.test_tab_change ✓                                                                                                                                                                                                    75% ███████▌  
 tests/test_integration.py::TestClass.test_grid_swap ✓                                                                                                                                                                                                    100% ██████████

Results (12.16s):
       4 passed
(venv)<Machine>:dash-app-kickstart <User>$ 

Our docker image is using Chrome v.67.0.3396.99-1, chromedriver v2.40.

[alexcjohnson]

I'll let @byronz comment on using the options, but I'll note a (sporadic) DevToolsActivePort file doesn't exist. is exactly why we added an auto-retry of starting the browser, most recent version #822 (comment) (included in dash 1.0.2)

If you're seeing a consistent failure, the options may be necessary; if it's sporadic the auto-retry may fix it.

[byronz]

@mmartinsky good point about the how-to, I added the issue for doc enhancement.

a sample hook, I put this in a conftest.py file under a submodule of tests folder

from selenium.webdriver.chrome.options import Options

def pytest_setup_options():
    """called before webdriver is initialized"""
    options = Options()
    options.add_argument('--no-sandbox')
    options.add_argument('--disable-dev-shm-usage')
    return options

and you can verify the options by increasing the logging level pytest -k dvui001 --log-cli-level DEBUG

Test session starts (platform: darwin, Python 3.7.4, pytest 4.6.4, pytest-sugar 0.9.2)
cachedir: .pytest_cache
rootdir: /Users/byron/code/dash, inifile: pytest.ini
plugins: sugar-0.9.2, mock-1.10.4, dash-1.0.1
collecting ...
------------------------------------------- live log setup --------------------------------------------
22:49:19 | DEBUG | selenium.webdriver.remote.remote_connection:388 | POST http://127.0.0.1:49395/session {"capabilities": {"firstMatch": [{}], "alwaysMatch": {"browserName": "chrome", "platformName": "any", "goog:chromeOptions": {"prefs": {"download.default_directory": "/private/var/folders/fl/dx4zhxfn11n3bbrrd7_hwhdr0000gn/T/pytest-of-byron/pytest-36/test_dvui001_disable_props_che0/download", "download.prompt_for_download": false, "download.directory_upgrade": true, "safebrowsing.enabled": false, "safebrowsing.disable_download_protection": true}, "extensions": [], "args": ["--no-sandbox", "--disable-dev-shm-usage"]}}}, "desiredCapabilities": {"browserName": "chrome", "version": "", "platform": "ANY", "loggingPrefs": {"browser": "SEVERE"}, "goog:chromeOptions": {"prefs": {"download.default_directory": "/private/var/folders/fl/dx4zhxfn11n3bbrrd7_hwhdr0000gn/T/pytest-of-byron/pytest-36/test_dvui001_disable_props_che0/download", "download.prompt_for_download": false, "download.directory_upgrade": true, "safebrowsing.enabled": false, "safebrowsing.disable_download_protection": true}, "extensions": [], "args": ["--no-sandbox", "--disable-dev-shm-usage"]}}}

we can tell that "args": ["--no-sandbox", "--disable-dev-shm-usage"]}}} is effective in selenium as configured in the hooks