test(pyamber): cover the source and batch operator final methods

[aglinxinyuan]

What changes were proposed in this PR?

test_operator.py goes from 32 tests to 44, covering SourceOperator.on_finish and BatchOperator's output-conversion arms.

Metric	Before	After
Codecov fully-covered lines today	173/183	178/183
Codecov fully-covered lines after #8040	171/183	178/183
Branch arms	26/30	30/30

+5 fully-covered lines today, +7 after #8040, and the file reaches 100% branch coverage. Lines 233 and 234 are line-hit with one arm untaken, so today's branch-less CI report already scores them covered; closing their second arm is mutation-proven but invisible until #8040 lands.

This is a small PR and I would rather say so than dress it up. What makes it worth having is that it closes the file permanently: the five remaining gap lines (153, 177, 259, 293, 515) are @abstractmethod bodies, and a grep of src/main/python for super().process_tuple|produce|process_batch|process_table|condition finds zero production call sites. 178/183 is the ceiling, so nobody needs to re-derive this target.

Scope narrowed during assessment, and the original plan is worth recording. This began as a three-file bundle also covering the four concrete partitioners and proxy_server.py. Both were dropped on measurement: the partitioners' base class is bare-pass stubs, and proxy_server.py is already at 90/95 with a 268-line spec, leaving 2 honest lines. Only operator.py survived.

What matters about the two covered paths

SourceOperator.on_finish is the uncovered production path of every Python source UDF. BatchOperator._process_batch's None and non-DataFrame arms decide what a batch operator emits when its handler returns nothing, or returns something that is not a DataFrame.

Verification

Measured from amber/ with the identical full-suite scope on both sides, --cov-branch passed explicitly (this branch lacks #8040's config), per-line hits and condition-coverage read out of coverage.xml by script rather than from the summary percentage. The before-state used main's spec extracted via git show HEAD: into a scratch dir and restored from that snapshot — never git restore.

Two reviewers returned nine findings against the first draft; all repaired. Three mutants survive and are reported rather than dropped, all three genuinely equivalent: != 0 to > 0 on a list length (non-negative by construction), and deleting @overrides.final from either method — overrides.final is typing.final, which enforces nothing at runtime. The last two prompted a docstring correction, since the original text claimed finality as the reason the method was worth testing.

Full pyamber suite: 5 failed, 1171 passed, 7 errors against main's 5 failed, 1159 passed, 7 errors. The FAILED/ERROR node-id sets were sorted and diffed — identical by identity, 12 entries. ruff check and ruff format --check pass on CI's exact scope. git diff --numstat is 226 0 — zero deletions.

No production file is touched; git diff -- 'amber/src/main/*' is empty.

Any related issues, documentation, discussions?

Closes #8043

How was this PR tested?

cd amber && python -m pytest -m "not integration" -q src/test/python/core/models/test_operator.py

44 passed, 1 warning

Was this PR authored or co-authored using generative AI tooling?

Generated-by: Claude Code (Opus 5)

[Copilot]

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[github-actions]

Automated Reviewer Suggestions

Based on the git blame history of the changed files, we recommend the following reviewers:

• Contributors with relevant context: @eugenegujing
  You can notify them by mentioning @eugenegujing in a comment.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.42%. Comparing base (b01b11f) to head (2c396d8).
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff            @@
##               main    #8047   +/-   ##
=========================================
  Coverage     93.41%   93.42%           
  Complexity     4696     4696           
=========================================
  Files          1179     1179           
  Lines         47713    47713           
  Branches       5314     5314           
=========================================
+ Hits          44573    44576    +3     
+ Misses         1698     1695    -3     
  Partials       1442     1442           

Flag	Coverage Δ		*Carryforward flag
access-control-service	81.00% <ø> (ø)		Carriedforward from b01b11f
agent-service	99.32% <ø> (ø)		Carriedforward from b01b11f
amber	89.60% <ø> (ø)		Carriedforward from b01b11f
computing-unit-managing-service	73.67% <ø> (ø)		Carriedforward from b01b11f
config-service	86.73% <ø> (ø)		Carriedforward from b01b11f
file-service	86.70% <ø> (ø)		Carriedforward from b01b11f
frontend	95.89% <ø> (ø)		Carriedforward from b01b11f
notebook-migration-service	79.31% <ø> (ø)		Carriedforward from b01b11f
pyamber	97.85% <ø> (+0.06%)	⬆️
workflow-compiling-service	77.19% <ø> (ø)		Carriedforward from b01b11f

*This pull request uses carry forward flags. Click here to find out more.

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[github-actions]

⚠️ Benchmark changes need a look

🟢 2 better · 🔴 2 worse · ⚪ 11 noise (<±5%) · 0 without baseline

Compared against main b01b11f benchmarked on this same runner, so the delta is largely free of cross-runner hardware noise. The "7d avg" column still reflects the gh-pages dashboard. Treat <±5% as noise unless repeated.

Dashboard · Run

	config	throughput	MB/s	latency	max Δ latest / 7d
🔴	bs=10 sw=10 sl=64	382	0.233	23,570/40,575/40,575 us	🔴 +14.6% / 🔴 +193.1%
🟢	bs=100 sw=10 sl=64	818	0.499	119,100/142,907/142,907 us	🟢 -16.8% / 🔴 +52.6%
⚪	bs=1000 sw=10 sl=64	938	0.572	1,065,257/1,117,696/1,117,696 us	⚪ within ±5% / 🔴 +23.9%

Baseline details

Latest main b01b11f from same runner

config	metric	PR	latest main	7d avg	Δ latest	Δ 7d
bs=10 sw=10 sl=64	throughput	382 tuples/sec	391 tuples/sec	894.86 tuples/sec	-2.3%	-57.3%
bs=10 sw=10 sl=64	MB/s	0.233 MB/s	0.239 MB/s	0.546 MB/s	-2.5%	-57.3%
bs=10 sw=10 sl=64	p50	23,570 us	23,043 us	11,139 us	+2.3%	+111.6%
bs=10 sw=10 sl=64	p95	40,575 us	35,399 us	13,843 us	+14.6%	+193.1%
bs=10 sw=10 sl=64	p99	40,575 us	35,399 us	16,839 us	+14.6%	+141.0%
bs=100 sw=10 sl=64	throughput	818 tuples/sec	797 tuples/sec	1,166 tuples/sec	+2.6%	-29.8%
bs=100 sw=10 sl=64	MB/s	0.499 MB/s	0.486 MB/s	0.711 MB/s	+2.7%	-29.9%
bs=100 sw=10 sl=64	p50	119,100 us	118,606 us	87,509 us	+0.4%	+36.1%
bs=100 sw=10 sl=64	p95	142,907 us	171,661 us	93,675 us	-16.8%	+52.6%
bs=100 sw=10 sl=64	p99	142,907 us	171,661 us	102,153 us	-16.8%	+39.9%
bs=1000 sw=10 sl=64	throughput	938 tuples/sec	930 tuples/sec	1,198 tuples/sec	+0.9%	-21.7%
bs=1000 sw=10 sl=64	MB/s	0.572 MB/s	0.568 MB/s	0.731 MB/s	+0.7%	-21.8%
bs=1000 sw=10 sl=64	p50	1,065,257 us	1,069,991 us	859,766 us	-0.4%	+23.9%
bs=1000 sw=10 sl=64	p95	1,117,696 us	1,174,820 us	902,897 us	-4.9%	+23.8%
bs=1000 sw=10 sl=64	p99	1,117,696 us	1,174,820 us	937,957 us	-4.9%	+19.2%

Raw CSV

config_idx,batch_size,schema_width,string_len,num_batches,total_ms,total_tuples,total_bytes,tuples_per_sec,mb_per_sec,lat_p50_us,lat_p95_us,lat_p99_us
0,10,10,64,20,523.87,200,128000,382,0.233,23569.68,40574.55,40574.55
1,100,10,64,20,2443.99,2000,1280000,818,0.499,119100.10,142907.38,142907.38
2,1000,10,64,20,21332.37,20000,12800000,938,0.572,1065256.98,1117696.39,1117696.39

[Copilot]

Pull request overview

Copilot reviewed 1 out of 1 changed files in this pull request and generated no new comments.

[mengw15]

LGTM