[enhancement] Only print performance variable reference values if defined

[jack-morrison]

Prior to change

A test without reference values prints (r:0, l:None, u:None) for each performance variable. This is #3175.

user@myhost:~/reframe-examples/tutorial$ reframe -c stream/stream_runonly.py -r
<snip>

[----------] start processing checks
[ RUN      ] stream_test /2e15a047 @generic:default+builtin
[       OK ] (1/1) stream_test /2e15a047 @generic:default+builtin
P: copy_bw: 136250.6 MB/s (r:0, l:None, u:None)
P: triad_bw: 127052.0 MB/s (r:0, l:None, u:None)
[----------] all spawned checks have finished

[  PASSED  ] Ran 1/1 test case(s) from 1 check(s) (0 failure(s), 0 expected failure(s), 0 skipped, 0 aborted)
[==========] Finished on Mon Jul 14 19:19:13 2025+0000
Log file(s) saved in '/tmp/rfm-wkcpor0o.log'

After change

A test without reference values does not print the reference tuple. Only the captured performance metric is printed.

user@myhost:~/reframe-examples/tutorial$ reframe -c stream/stream_runonly.py -r
<snip>

[----------] start processing checks
[ RUN      ] stream_test /2e15a047 @generic:default+builtin
[       OK ] (1/1) stream_test /2e15a047 @generic:default+builtin
P: copy_bw: 124658.9 MB/s
P: triad_bw: 99002.0 MB/s
[----------] all spawned checks have finished

[  PASSED  ] Ran 1/1 test case(s) from 1 check(s) (0 failure(s), 0 expected failure(s), 0 skipped, 0 aborted)
[==========] Finished on Mon Jul 14 19:13:53 2025+0000
Log file(s) saved in '/tmp/rfm-_jygclgm.log'

A test with reference values behaves as before. The captured performance metric and its references are both printed.

user@myhost:~/reframe-examples/tutorial$ reframe -c stream/stream_runonly.py -r
<snip>

[----------] start processing checks
[ RUN      ] stream_test /2e15a047 @generic:default+builtin
[       OK ] (1/1) stream_test /2e15a047 @generic:default+builtin
P: copy_bw: 133880.3 MB/s (r:137659, l:-0.1, u:0.3)
P: triad_bw: 129926.7 MB/s (r:137659, l:-0.55, u:0.5)
[----------] all spawned checks have finished

[  PASSED  ] Ran 1/1 test case(s) from 1 check(s) (0 failure(s), 0 expected failure(s), 0 skipped, 0 aborted)
[==========] Finished on Mon Jul 14 19:14:31 2025+0000
Log file(s) saved in '/tmp/rfm-2md5inu3.log'

Closes #3175

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 91.38%. Comparing base (b57f957) to head (ba9a711).
Report is 36 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #3517      +/-   ##
===========================================
+ Coverage    91.16%   91.38%   +0.22%     
===========================================
  Files           62       62              
  Lines        13253    13360     +107     
===========================================
+ Hits         12082    12209     +127     
+ Misses        1171     1151      -20     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[vkarak]

I would change the check here to

Suggested change

	if ref is not None and lower is not None and upper is not None:
	if ref is not None:

Because otherwise it will mask out cases where the reference is set, but not the thresholds. Also are you sure that checking the reference against None is correct. I think when it's missing we are setting it to 0:

reframe/reframe/core/pipeline.py

Line 2440 in e3c4b30

ref = (0, None, None)