chore: minor test cleanups

Signed-off-by: Rudi Grinberg <me@rgrinberg.com>

Author: rgrinberg

test/blackbox-tests/test-cases/cram/subprocess.t

@@ -7,8 +7,7 @@ project with a single cram test.
 
 We create a file for tracking the PID of a subprocess.
 
-  $ cat > pid.txt
-  $ export FILE=$(realpath ./pid.txt)
+  $ FILE=$(realpath ./pid.txt)
 
 We create a cram test that spawns a subprocess and records its PID in the file
 we gave before.
@@ -20,10 +19,12 @@ we gave before.
 
 We can now run this test, which will record its PID in the file.
 
-  $ dune build @mycram
+  $ dune runtest mycram.t
 
 The test finished successfully, now we make sure that the PID was correctly
 terminated.
 
+  $ [ -s $FILE ] && echo pid file created
+  pid file created
   $ ps -p $(cat $FILE) > /dev/null || echo "Process terminated"
   Process terminated