Notice that if the string the constituency of which you want to test is already at the very beginning of the sentence, then you cannot perform the test, because leftward movement is impossible. If the sentence you get as a result is grammatical and can have the same interpretation as the sentence you started out with, then the test was successful. If the test was not successful, you do not know whether the original string of words was a constituent. The test was successful. Thus, 'our new car' is a constituent.
Man is the in the bathroom.
This is not a grammatical sentence. The test fails. No conclusions are warranted. This is certainly a well-formed sentence of English, but it cannot mean the same thing as the original sentence. The test failed and no firm conclusions can be drawn.