test(amber): add unit test coverage for FutureBijection and ElidableStatement

[aglinxinyuan]

What changes were proposed in this PR?

Pin behavior of two utility modules in engine/common. No production-code changes.

Spec	Source class	Tests
FutureBijectionSpec	FutureBijection	11
ElidableStatementSpec	ElidableStatement	9

Both spec files follow the <srcClassName>Spec.scala one-to-one convention.

Behavior pinned — FutureBijection

Surface	Contract
TwitterFuture.value.asScala	resolves to the same value (type preserved, null preserved)
TwitterFuture.exception.asScala	resolves with the same Throwable instance (type, message, eq identity)
ScalaFuture.successful.asTwitter	resolves to the same value (type preserved, null preserved)
ScalaFuture.failed.asTwitter	resolves with the same Throwable instance
Twitter → Scala on an already-resolved future	the resulting Scala future is already completed when the implicit returns
Twitter → Scala → Twitter round-trip	preserves both values and exceptions
Scala → Twitter → Scala round-trip	preserves values

Behavior pinned — ElidableStatement

The texera build sets -Xelide-below WARNING (amber/build.sbt). Every ElidableStatement helper is annotated with an elide level strictly below WARNING (FINEST / FINER / FINE / INFO), so the Scala compiler replaces every CALL to these helpers with a () Unit value at compile time. The spec pins this silent-in-production contract:

Surface	Contract
info / fine / finer / finest (with side-effect block)	the side effect MUST NOT fire (counter stays at 0)
same methods (with throwing block)	the exception MUST NOT propagate
1000 successive elided calls	no side-effect accumulation
Return type	Unit (compile-time enforced)
Parameter shape	accepts a => Unit by-name block (compile-time enforced)

A regression that bumped a method's elide level above WARNING, removed the @elidable annotation, or relaxed -Xelide-below in the build would re-enable side effects in production — and this spec would catch it.

Any related issues, documentation, discussions?

Closes #5551.

How was this PR tested?

Pure unit-test additions; verified locally with:

• sbt "WorkflowExecutionService/testOnly org.apache.texera.amber.engine.common.FutureBijectionSpec org.apache.texera.amber.engine.common.ElidableStatementSpec" — 20 tests, all green
• sbt scalafmtCheckAll — clean
• CI to confirm

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

Generated-by: Claude Code (Sonnet 4.5)

[Copilot]

Pull request overview

This PR adds ScalaTest unit specs under amber/src/test/scala/.../engine/common to pin and regress-test the behavior of two small but widely used utility modules (FutureBijection and ElidableStatement) in Amber’s common engine layer, without changing production code.

Changes:

• Add FutureBijectionSpec covering Twitter Future ↔ Scala Future conversions for success/failure/null and round-trip behavior.
• Add ElidableStatementSpec ensuring @elidable helpers remain compile-time-elided under -Xelide-below WARNING, so side-effecting/throwing blocks do not execute.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
amber/src/test/scala/org/apache/texera/amber/engine/common/FutureBijectionSpec.scala	Adds unit coverage for Twitter↔Scala Future conversions, including null/exception identity and round-trips.
amber/src/test/scala/org/apache/texera/amber/engine/common/ElidableStatementSpec.scala	Adds unit coverage that elided logging helpers remain no-ops under the project’s -Xelide-below WARNING setting.

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[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 52.14%. Comparing base (afc5f98) to head (a297c1a).
⚠️ Report is 2 commits behind head on main.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #5555      +/-   ##
============================================
+ Coverage     52.09%   52.14%   +0.04%     
- Complexity     2471     2479       +8     
============================================
  Files          1067     1067              
  Lines         41273    41273              
  Branches       4437     4437              
============================================
+ Hits          21502    21520      +18     
+ Misses        18509    18490      -19     
- Partials       1262     1263       +1     

Flag	Coverage Δ		*Carryforward flag
access-control-service	64.61% <ø> (ø)		Carriedforward from afc5f98
agent-service	33.76% <ø> (ø)		Carriedforward from afc5f98
amber	53.23% <ø> (+0.11%)	⬆️
computing-unit-managing-service	1.65% <ø> (ø)		Carriedforward from afc5f98
config-service	56.06% <ø> (ø)		Carriedforward from afc5f98
file-service	38.32% <ø> (ø)		Carriedforward from afc5f98
frontend	46.40% <ø> (ø)		Carriedforward from afc5f98
pyamber	90.69% <ø> (ø)		Carriedforward from afc5f98
python	90.83% <ø> (ø)		Carriedforward from afc5f98
workflow-compiling-service	58.69% <ø> (ø)		Carriedforward from afc5f98

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

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