Is there a quick and easy way to test water that one may come across in a post-SHTF situation? I know I should take Hollywood with a block of salt, but I remember that at the beginning of The Postman, Kevin Costner's character tests some standing water using a small test kit.

This appears to be just a simple PH test kit available at any store that sells aquarium products. If so, it would really only tell the user if the water was basic or acidic. Nothing regarding POL contaminants or biological pathogens.

WITHOUT going into the various methods of filtration, are there any better ideas for testing water quickly and easily?

On equipment: You get what you inspect, not what you expect.
On training: Our drills are bloodless battles so that our battles are bloody drills.
On tactics: Cheating just means you're serious about winning.