Custom wait conditions in Selenium Python - Build an Automation Script

Wait for a specific element's text to change before proceeding

Preconditions (2)

Step 1: Navigate to the target web page URL

Step 2: Locate the element with id 'status-message'

Step 3: Wait until the text of the element changes from 'Loading...' to 'Complete'

Step 4: Verify that the element's text is exactly 'Complete'

✅ Expected Result: The test waits until the element's text changes to 'Complete' and then verifies it successfully

Automation Requirements - Selenium with Python

Assertions Needed:

Assert the element's text is 'Complete' after waiting

Best Practices:

Use WebDriverWait with a custom expected condition

Avoid using time.sleep for waiting

Use By.ID locator for element identification

Handle TimeoutException properly

Automated Solution

Selenium Python

from selenium import webdriver
from selenium.webdriver.common.by import By
from selenium.webdriver.support.ui import WebDriverWait
from selenium.webdriver.support import expected_conditions as EC
from selenium.common.exceptions import TimeoutException

class text_to_be_changed:
    def __init__(self, locator, old_text):
        self.locator = locator
        self.old_text = old_text

    def __call__(self, driver):
        element = driver.find_element(*self.locator)
        if element.text != self.old_text:
            return element
        else:
            return False

def test_wait_for_text_change():
    driver = webdriver.Chrome()
    driver.get('https://example.com/dynamic-text')

    locator = (By.ID, 'status-message')
    old_text = 'Loading...'

    wait = WebDriverWait(driver, 10)
    try:
        element = wait.until(text_to_be_changed(locator, old_text))
        assert element.text == 'Complete', f"Expected text 'Complete' but got '{element.text}'"
    except TimeoutException:
        assert False, "Timed out waiting for text to change"
    finally:
        driver.quit()

The text_to_be_changed class is a custom wait condition that waits until the text of the element located by locator changes from old_text. It returns the element when the text changes, otherwise returns False to keep waiting.

In the test function, we open the browser and navigate to the page. We define the locator for the element with id status-message and the old text Loading....

We use WebDriverWait with our custom condition to wait up to 10 seconds for the text to change. If the text changes, we assert it is exactly Complete. If the wait times out, we fail the test with a clear message.

Finally, we close the browser to clean up.

Common Mistakes - 3 Pitfalls

Using time.sleep() instead of explicit waits

Hardcoding XPath locators that are brittle

Not handling TimeoutException

Bonus Challenge

Now add data-driven testing with 3 different old texts to wait for changes

Show Hint

Practice

1. What is the main purpose of creating a custom wait condition in Selenium with Python?

easy

A. To automatically retry failed tests

B. To speed up the test execution by skipping waits

C. To replace the WebDriverWait class completely

D. To wait for a specific condition that is not covered by built-in waits

Solution

1. Step 1: Understand built-in waits limitations

   Built-in waits cover common cases but sometimes you need to wait for a unique condition.

2. Step 2: Purpose of custom wait

   Custom waits let you define exactly what to wait for, improving test reliability.

3. Final Answer:

   To wait for a specific condition that is not covered by built-in waits -> Option D

4. Quick Check:

   Custom wait = wait for unique condition [OK]

Hint: Custom waits handle unique conditions not in built-in waits [OK]

Common Mistakes:

• Thinking custom waits speed up tests
• Believing custom waits replace WebDriverWait
• Assuming custom waits retry tests automatically

2. Which of the following is the correct way to define a custom wait condition class in Selenium Python?

easy

A. class MyWait:
def __call__(self, driver):
return driver.find_element_by_id('myid')

B. class MyWait:
def wait(self):
return True

C. def MyWait(driver):
return driver.find_element('id', 'myid')

D. class MyWait:
def wait_for(self, driver):
return False

Solution

1. Step 1: Identify the special method for custom waits

   Custom wait classes must implement the __call__ method to be callable by WebDriverWait.

2. Step 2: Check method signature and return

   Method __call__ takes driver and returns element or True when condition met.

3. Final Answer:

   class MyWait:\n def __call__(self, driver):\n return driver.find_element_by_id('myid') -> Option A

4. Quick Check:

   Custom wait uses __call__ method [OK]

Hint: Custom wait class must have __call__(self, driver) method [OK]

Common Mistakes:

• Using method named wait instead of __call__
• Defining function instead of class
• Using wrong method signature

3. Given the code below, what will be the output if the element with id 'submit' appears after 3 seconds?

from selenium.webdriver.support.ui import WebDriverWait
from selenium.webdriver.common.by import By

class WaitForSubmit:
    def __call__(self, driver):
        try:
            elem = driver.find_element(By.ID, 'submit')
            return elem
        except:
            return False

wait = WebDriverWait(driver, 5)
submit_button = wait.until(WaitForSubmit())
print(submit_button.tag_name)

medium

A. Prints False

B. Raises TimeoutException immediately

C. Prints the tag name of the 'submit' element after waiting

D. Raises NoSuchElementException

Solution

1. Step 1: Understand the custom wait behavior

   The custom wait tries to find element with id 'submit'. If not found, returns False to keep waiting.

2. Step 2: Analyze wait.until with timeout 5 seconds

   The element appears after 3 seconds, so wait.until returns the element before timeout.

3. Final Answer:

   Prints the tag name of the 'submit' element after waiting -> Option C

4. Quick Check:

   Element appears before timeout, so tag_name prints [OK]

Hint: Custom wait returns element or False; wait.until waits until element found [OK]

Common Mistakes:

• Assuming immediate TimeoutException
• Expecting print of False instead of element
• Confusing exceptions raised

4. Identify the error in the following custom wait condition code:

class WaitForText:
    def __call__(self, driver):
        element = driver.find_element(By.ID, 'message')
        if element.text == 'Done':
            return True
        else:
            return None

wait = WebDriverWait(driver, 10)
wait.until(WaitForText())

medium

A. Returning None instead of False causes wait.until to stop waiting

B. Missing import for By causes NameError

C. Returning True instead of element causes error

D. Using find_element instead of find_elements causes exception

Solution

1. Step 1: Check imports

   The code uses By.ID but does not import By, causing NameError at runtime.

2. Step 2: Analyze return values

   Returning True or None is allowed; wait.until treats True as success and None as failure to continue waiting.

3. Final Answer:

   Missing import for By causes NameError -> Option B

4. Quick Check:

   By must be imported to avoid NameError [OK]

Hint: Always import By before using it in locators [OK]

Common Mistakes:

• Thinking None stops waiting (it continues)
• Assuming returning True causes error
• Confusing find_element with find_elements

5. You want to wait until a button with id 'start' is both visible and enabled before clicking it. Which custom wait condition class correctly implements this?

hard

A. class WaitForStart:
def __call__(self, driver):
btn = driver.find_element(By.ID, 'start')
if btn.is_displayed() and btn.is_enabled():
return btn
return False

B. class WaitForStart:
def __call__(self, driver):
btn = driver.find_element(By.ID, 'start')
if btn.is_displayed() or btn.is_enabled():
return True
return False

C. class WaitForStart:
def __call__(self, driver):
btn = driver.find_element(By.ID, 'start')
if btn.is_displayed() and btn.is_enabled():
return True
return False

D. class WaitForStart:
def __call__(self, driver):
btn = driver.find_element(By.ID, 'start')
if btn.is_enabled():
return btn
return None

Solution

1. Step 1: Check condition logic

   We need both visible and enabled, so use 'and' operator to check both.

2. Step 2: Return element when condition met

   Return the button element so wait.until returns it for further actions.

3. Final Answer:

   class WaitForStart:\n def __call__(self, driver):\n btn = driver.find_element(By.ID, 'start')\n if btn.is_displayed() and btn.is_enabled():\n return btn\n return False -> Option A

4. Quick Check:

   Return element when visible and enabled [OK]

Hint: Return element only if visible AND enabled, else False [OK]

Common Mistakes:

• Using 'or' instead of 'and' for conditions
• Returning True instead of element
• Returning None instead of False