Your manufacture will send you samples of your product throughout various stages in the process. This allows you to analyze your product before you begin mass production.
There are three types of samples:
1) White Sample
This sample involves no artwork, only the actual components. This sample is created earlier on in the process. This allows you to see the quality of the components you have selected. And allows you to see if everything fits inside the box. You're basically handed a blank version of your game.
2) Digital Sample
This sample involves your artwork, but the art is printed using normal printers (not the mass production printers). So the color is not truly accurate, but maybe 90% accurate. The product is also quickly assembled by hand, so not everything will be perfectly executed.
3) Offset Sample
This is basically your mass production sample, which is made using the offset printers (the same used for actual production). The product might still be assembled by hand, but the art will be 100% accurate in color.
My manufacturer has included this guidebook that discusses all the aspects of creating samples: