I was on the job market recently and similar things happened to me. It's worse when you don't get feedback after you go to an interview.
Two days ago I thought of making a job site that requires the employer to provide feedback, and the candidate to sign a form that says they won't sue the employer over the interview process. This way the employer has no excuse for not giving feedback.
I see very little value for the company in agreeing to something like this. A user could still sue (even after signing the form) by claiming the given feedback is discriminatory or something similar. No company would voluntarily take on that sort of liability when there are countless alternatives.
I've had things like this happen more than once:
1. HR/recruiter-ish Phone screening
2. Engineer-ish phone screening, sometimes with a coding session
3. Another phonecall as a prep for further rounds of interviews
4. Travel that requires me to take at least one day off of work and travel to another city for an in-person interview
5. Rejection with no reason, and "We have a policy of not providing that information to candidates" if you ask why
6. Questionnaire from the company, asking for feedback on their interview process (snerk)
In your case, with one guess, I'd say that the test cases that were provided were just examples of things you'd have to do to pass. It's like the homework assignment where the professor gives you a problem to solve and some test inputs. You know that they'll run some "acid test" on your code after you've submitted it. Maybe it caught some corner cases that they considered essential.
That, or they didn't like something about your coding style (style is subjective, and you'll never have feedback on how they judged it). Or, or, or...you can come up with speculative lists all day.
4. This in some ways is worse than greyostrich's situation (because it cost you more), but in another way, it's better. It cost the company, too - the cost of the flight, hotel, and time for their people to interview you. They didn't just waste your time to try to spare themselves any effort; they had skin in the game too.
5. In the current legal climate, if they tell you why, they may be exposing themselves to a lawsuit. They therefore impose a company-wide policy of never saying why they reject anyone. It stinks for the rejected applicant, but it's not because they're being jerks to the rejected applicant. It's because of lawyers. If you want to fix it, you're going to have to fix the law.
Two days ago I thought of making a job site that requires the employer to provide feedback, and the candidate to sign a form that says they won't sue the employer over the interview process. This way the employer has no excuse for not giving feedback.
Would you use this?