Couldn't run a test-app. Please Help me

I’m using the Deepstream 4.x

I had the same problem…
you must go to : “/opt/nvidia/deepstream-4.0/sources/apps/sample_apps/deepstream-test1”
over there u will see a bunch of files:

    c file dstest1_pgie_config.txt a Make file a readme file

you compile by just typing : make
normally you should see a new file.

then you run:
./deepstream-test1-app /opt/nvidia/deepstream/deepstream-4.0/samples/streams/sample_720p.h264
" et voilà!"
hope it helps - for me it did