fix #2583: fix negative and asymmetric edge costs in stoer wagner tests

[prashsti29]

Fixes #2583

Changes proposed in this pull request:

• Ensures edge costs and reverse_costs are non-negative and symmetric before running Stoer-Wagner tests
• Fixes test failures caused by negative and asymmetric edge weights which violate Stoer-Wagner algorithm requirements

@pgRouting/admins

Summary by CodeRabbit

• Tests
  • Updated minimum-cut tests to normalize edge costs to non-negative values so negative inputs now map to positive representations.
  • Tightened a test input filter to target a smaller set of edges during an error assertion, improving test precision.

[coderabbitai]

Walkthrough

Updates Stoer–Wagner test scripts to normalize edges.cost and edges.reverse_cost using abs(sign(...)) instead of sign(...), making stored normalized values non-negative; also adjusts one pgr_stoerWagner call filter in edge_cases.pg.

Changes

Cohort / File(s)	Summary
Stoer–Wagner cost normalization pgtap/mincut/stoerWagner/compare_components.pg, pgtap/mincut/stoerWagner/inner_query.pg, pgtap/mincut/stoerWagner/types_check.pg	Changed test setup to write edges.cost and edges.reverse_cost as abs(sign(...)) instead of sign(...), ensuring normalized values are 0 or 1 (negative inputs now map to 1).
Edge-case test & query filter pgtap/mincut/stoerWagner/edge_cases.pg	Same abs(sign(...)) normalization change; also modified a pgr_stoerWagner call filter to use WHERE id < 17 (replacing the prior FROM edges id < 17 form).

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Suggested reviewers

• cvvergara
• robe2

Poem

🐇 I hopped through tests with whiskers keen,

Turned signs to absolutes, tidy and clean,
No negatives hiding where edges roam,
Now cuts and paths have a brighter home.

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately describes the main objective of the PR: fixing negative and asymmetric edge costs in Stoer-Wagner tests, which aligns with all four modified test files.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[coderabbitai]

Caution

Some comments are outside the diff and can’t be posted inline due to platform limitations.

⚠️ Outside diff range comments (1)

pgtap/mincut/stoerWagner/edge_cases.pg (1)

17-22: 🧹 Nitpick | 🔵 Trivial

Pre-existing SQL syntax issue in the test query.

The inner query has a missing WHERE keyword: FROM edges id < 17 should be FROM edges WHERE id < 17. While this test passes because it expects the function signature error (function with 2 args doesn't exist), the SQL error would occur first if the function signature matched.

This is a pre-existing issue unrelated to this PR's changes.

Suggested fix for the SQL syntax

 SELECT throws_ok(
     'SELECT * FROM pgr_stoerWagner(
-        ''SELECT id, source, target, cost, reverse_cost FROM edges id < 17'',
+        ''SELECT id, source, target, cost, reverse_cost FROM edges WHERE id < 17'',
         3
     )','42883','function pgr_stoerwagner(unknown, integer) does not exist',
     '6: Documentation says it does not work with 1 flags');

🤖 Prompt for AI Agents

Verify each finding against the current code and only fix it if needed.

In `@pgtap/mincut/stoerWagner/edge_cases.pg` around lines 17 - 22, The test
contains a SQL syntax error in the inner query of the SELECT throws_ok call:
replace the malformed fragment "FROM edges id < 17" with a proper WHERE clause
so the inner query is "SELECT id, source, target, cost, reverse_cost FROM edges
WHERE id < 17"; update the test that invokes pgr_stoerWagner (the SELECT
throws_ok wrapping pgr_stoerWagner call) to use the corrected inner SQL so the
intended function-signature error remains the first possible error when
appropriate.

🤖 Prompt for all review comments with AI agents

Verify each finding against the current code and only fix it if needed.

Outside diff comments:
In `@pgtap/mincut/stoerWagner/edge_cases.pg`:
- Around line 17-22: The test contains a SQL syntax error in the inner query of
the SELECT throws_ok call: replace the malformed fragment "FROM edges id < 17"
with a proper WHERE clause so the inner query is "SELECT id, source, target,
cost, reverse_cost FROM edges WHERE id < 17"; update the test that invokes
pgr_stoerWagner (the SELECT throws_ok wrapping pgr_stoerWagner call) to use the
corrected inner SQL so the intended function-signature error remains the first
possible error when appropriate.

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: Repository UI

Review profile: ASSERTIVE

Plan: Pro

Run ID: d2ee35b1-a4d2-4422-a2cb-3f2a4e98ec3d

📥 Commits

Reviewing files that changed from the base of the PR and between e06c177 and 0d93eff.

📒 Files selected for processing (4)

• pgtap/mincut/stoerWagner/compare_components.pg
• pgtap/mincut/stoerWagner/edge_cases.pg
• pgtap/mincut/stoerWagner/inner_query.pg
• pgtap/mincut/stoerWagner/types_check.pg