WebDriver Test Rule is a way of performing further actions based on the results of a test. Assuming that a test a failed then we can write a rule to run certain actions when a test failures occurs. These tests rules are not subject to test failures only but are available for multiple test completions methods.
WebDriver Test Rule Video Tutorial
Test Rules can help to run additional methods which only run depending on the outcome of a test. This can be used to further help our test application in providing support code for our tests.