The worst thing you can do, as a designer, is hesitate to show someone your work in progress. It’s not fun, it’s not exciting, it doesn’t work right, it’s not even complete–all of that is fine. Everyone understands that creators need feedback, and by and large I’ve found people very willing to be a part of that. There’s nothing wrong with testing a game before it’s “ready,” so don’t be shy about doing so.
Once every so often I run into someone who feels reluctant to playtest until a game is done. Sometimes this is a matter of pride for them, but more often it comes from a worry about wasting the players’ time. Dropping a bad game in their lap feels like doing them an unkindness.
In my experience, though, people like playtesting. They enjoy the feeling of being an insider, of seeing behind the curtain. What was opaque becomes something they can interact with, and that’s exciting.
What’s more, people just plain like being helpful. If you ask for assistance with testing they’re often happy to oblige. There’s no imposition in help freely given.
Of course, there are some limits. It’s good to make reasonable preparations for your playtesters: have necessary components ready to go, and think through how you’re going to explain the rules (or have the rulebook ready for them, if you’re at that point). The game failing isn’t a waste of the playtesters’ time–that’s part of testing–but being unprepared might be.
So, be courteous–but don’t be reluctant. Playtesting is necessary for you, and often engaging for the testers. Rather than denying them the fun of approaching a game in an unusual way, run your idea out there and see how it goes.