There are two main types of drug test that are easy enough to use at home or at work.  They are mouth swab - where the test is held in the mouth and absorbs saliva and detects drugs present.  Or urine dip tests that get dipped in a 'cup' of urine from the person being tested and detect drugs.

Both have pros and cons.

Pros for Oral swab tests

• don't require collection of urine and can be done quickly
• little mess and there no cup of urine to dispose of afterwards. 
• detect drugs much quicker than urine based tests.   For instance methamphetamine (or P) in as little as 5 minutes. 
• it's difficult to adulterate/contaminate sample to invalidate the test.
• Can be more effective in detecting recent marijuana use in people who haven't previuosly used it. *

Pros for Urine tests

• longer windows of detection up to 30 days for THC 
• can detect lower levels of drugs - particularly methamphetamine (P)*
• fewer false negatives *

Neither give a number for amount or concentration of drug in the body.  Blood tests are required for that.

Click here for information on how long various drugs are detectable.

*https://pubmed.ncbi.nlm.nih.gov/27344042/