Too Long; Didn't Read
According to <a href="https://en.wikipedia.org/wiki/Test-driven_development" target="_blank">Wikipedia</a>, it means “Requirements are turned into very specific <a href="https://en.wikipedia.org/wiki/Test_case" title="Test case" target="_blank">test cases</a>, then the software is improved to pass the new tests, only.” Basically, you would first have to write the test of the software/feature you are developing before you start working on the developing the software/feature itself.