Here's "poorman's compression test" that can be applied to diesel engines:

Crank the engine in cold-start mode on warm day WITHOUT warming up glow plugs. Keep crankin and crankin..... and if engine is extremely tight - the diesel will start on compression alone!!

This does not mean the engine is played if it wont start eventually after lotsa cranking without warming glowplugs.... but truely exceptional engines will pass this test.

-Just one of several tests on buying a diesel.....

Another is to ask the seller to fire up the car in regular cold-start mode while you observe smoke while standing near the tailpipe. Normal cold-start smoke should quickly disappear as the car warms up.

Also ask about oil consumption.... 1 qt. (or liter?) in 500 - 1200 miles (dunno the kilometer equivalent) is entirely acceptable.