How do the Verify and Assert commands differ in Selenium?

In the automation testing framework Selenium, the Verify and Assert commands are both used to validate the state of an application, but they differ in how they handle failures.

Assert Commands

• Assert commands are used for critical checkpoints that must be satisfied. If the condition in an Assert command fails, the test execution halts immediately, as this command causes the test to stop at the point of failure. This is because Assert typically checks essential parts of the test; if these fail, continuing the test is meaningless.

For example, when testing an e-commerce website, using Assert to validate the login functionality is appropriate because if login fails, subsequent steps like adding items to the cart and checkout cannot proceed.

python
assert "Welcome, username" in driver.page_source

Verify Commands

• Verify commands are also used to validate the application's state, but even if the condition fails, the test execution does not halt. Verify is suitable for non-critical checkpoints where failure does not interrupt the test flow.

For example, when testing for the presence of a copyright notice at the bottom of a webpage, even if this information is missing or incorrect, it typically does not affect the user's ability to perform core business processes such as browsing products and adding items to the cart. Thus, using Verify is more appropriate in this case.

python
try:
    assert "Copyright" in driver.page_source
except AssertionError:
    print("Copyright information is incorrect")

Summary

In summary, Assert is suitable for critical assertions in the test flow where failure typically means subsequent steps cannot proceed. Verify is appropriate for non-critical checkpoints where failure does not affect the overall test flow. When writing automated test scripts, choosing between Assert and Verify based on the purpose and importance of the test is crucial.