If the base URL succeeds, but a later object results in a 404 response code, the test result for the entire page is marked successful.
A Synthetic Classic test fails when a base URL request for a step (or sequence) in the test receives only a 404 (file not found) response. However, if the 404 response redirects the browser to another object that downloads successfully, the test results for the page are considered successful. Likewise, if the base URL for a page succeeds, but a later object returns a 404 response code, then the test results for the entire page are considered successful.
If you want the test to fail if an object fails to download even though the base page is downloaded successfully, configure one or more content matches in the test script. For details, see Validate script action in the documentation.
You can configure one or more Object Failure alerts when you provision a Backbone test. For details, see Backbone alert settings in the documentation.