I know this lady seems awful, but the concept of a "tester" extends to other issues where invalidating the concept basically allows the illegal behavior to exist unchecked.
Let's use the example of a bar that has a locally known, but unwritten, rule against allowing in black patrons. This isn't legal. But you can't really bring suit unless an unfamiliar black traveler tries to stumble into the bar, only to be told they're not allowed. Or someone who knows the unwritten rule exists can go to get denied, thereby providing actionable proof of discrimination for a lawsuit.
And there's a solid 50% chance that I will not answer that call