Well first of all it is a good, no really great, idea to have a good idea! Sounds silly but many ideas are just that.
I could have a really great idea about growing bananas underwater but something tells me that I would be wasting my time.
When the go/no go decision is a little less obvious we must be a little more logical about testing for a good idea.
Here are ten suggestions as to how to test your idea:

1. What problem (or business pain) is your idea targeted at?
2. Is your idea well formed or do you have more work to do?
3. Do you understand why your idea will appeal to potential customers?
4. When you tell people about your idea do they get it immediately?
5. Do you have a prototype or have you conducted a trial? Have you received positive feedback?
6. Have you costed your idea, what will you sell it for?
7. How will you make your product or deliver your service?
8. Do you have the necessary skills and resources or will you buy them (where from)?
9. Have you checked that nobody has done this before?
10. Do you wish to retain ownership of your idea?

You may well have further tests in an organisation specific context e.
g.
does this fit with strategy or existing products but these are a good starting point.
It is always best to test your ideas to avoid wasting time in a commercial environment.
If not you may simply be playing and wasting your time.