4-point quick cannabis inspection test that may help to identify common cannabis scams:

1. Visual Check

Buds should be a decent density with large brown pistils and a generally crystal appearance. If it looks like bagged up grass ditch it!

2. Nose test

Some bud sold in the UK does not smell of anything at all so check for this.

The scent of Cannabis is extremely complex and varies according to strain and terpine content, however it can usually be instantly identified... If there is cannabis smell, contain yourself and proceed with the utmost of caution!

3. Moisture Test

Check the moisture content of the weed. Good weed should be dry but resinous.  A common guide for testing for dampness is to bend a twig, which should easily snap and the bud should break up reasonably easily rather than rolling up into a big lump that needs to be torn up. If it's bone-dry dusty it's almost certainly not worth proceeding as next test will almost certainly fail.

4. Oil Test

Good cannabis should leave resin behind on things :) This should be evident on the inside of the bag it is in or after rubbing on a piece of glass. However, pretty much all cannabis for sale has had some amount of shaking done to it, which is to be expected unless explicitly sold top-grade bud. Despite the common practice of shaking bud prior to sale, a little agitation of the bud in the bag should leave visible traces of resin inside the bag, alternatively break a small bud and rub the broken surface on a piece of clear glass.   If the bag/glass appears totally clean then it's probably been messed with. If still unsure try breaking a piece of bud and pinch the freshly broken piece between your fingers, then rub your fingers together... if your fingers feel clean then proceeding will probably only lead to disappointment!

5. Have a Closer Look

Although i've not yet seen bad quality cannabis that can pass test 4, it is foreseeable that rip-off dealers and growers will work out a way to do it before long, however it is unlikely that it will ever be possible and cost effective to apply "stuff" to buds in a way that replicates the natural trichome structure of cannabis so close-up visual inspection is probably one of the best tests that can be performed at home, and will identify other contaminants such as grit or mold.

A decent DSL-R camera can show up detail that would not be visible from the eye so may help but really a 10x-30x jewelers loupe or microscope is needed to inspect the trichome structure of the cannabis. Check:

Good Bud Shit Weed
Tricomes: tiny hairs that wick up oils from the plant to form a distinctive stalk with a head on the top big lumps of crystalised stuff on the buds
The tricomes should be fairly evenly distributed signs that the entire bud or leaf is coated

6. Column Chromatography

Blah blah blah

If in doubt Bin It!