De or het testinspanning?

The correct Dutch article is:

de testinspanning

Rule Words ending in -ing: almost always de. See the rule

How to use testinspanning

the testinspanningde testinspanning
this testinspanningdeze testinspanning
that testinspanningdie testinspanning
our testinspanningonze testinspanning
your testinspanningjouw testinspanning
every testinspanningelke testinspanning
which testinspanning?welke testinspanning?
a big testinspanning / the big testinspanningeen grote testinspanning, de grote testinspanning