[tests] Fixed flaky test_topology_graph

[youhaveme9]

Checklist

• I have read the OpenWISP Contributing Guidelines.
• I have manually tested the changes proposed in this pull request.
• I have written new test cases for new code and/or updated existing tests for changes to existing code.
• I have updated the documentation.

Reference to Existing Issue

Closes #347

Please open a new issue if there isn't an existing issue yet.

[pandafy]

Let's assume that the TimeoutError is raised by this code. I would update the logic here

Suggested change

	element = WebDriverWait(driver, 10).until(
	EC.presence_of_element_located((By.XPATH, path))
	)
	try:
	element = WebDriverWait(driver, 10).until(
	EC.presence_of_element_located((By.XPATH, path))
	)
	except Exception:
	import ipdb
	ipdb.set_trace()

The test execution will halt when the code in except block is executed. Now, inspect the webpage. open the JS console on browser (created by selenium) and look for any errors.

[pandafy]

From the development chat by @youhaveme9

Running the test manually always passes
But running the test continuously in a loop using a script sometimes throws a timeout error
Is it due to the WebDriverWait function or something else?

@youhaveme9 you're correct. The TimeoutError appears because WebDriverWait cannot find the element in the defined time period.

For debugging, I suggest the following:

1. Don't run the test suite with SELENIUM_HEADLESS. Change the headless key to false, so you will observe what selenium is doing with the web browser.

docker-openwisp/tests/config.json

Line 3 in b0bcaed

"headless": true,

2. When running the test suite in loop, pause the execution with ipdb so you can inspect the problematic webpage. (You will need to install ipdb with pip install ipdb in your venv)