Port TraceMapperV0_4/V0_5 payload tests from Spock to JUnit 5

[dougqh]

What

Migrates TraceMapperV04PayloadTest and TraceMapperV05PayloadTest from Groovy/Spock to JUnit 5 Java. TraceMapperV1PayloadTest and TraceMapperTest are left untouched (V1 is newer and not yet in production — deferred).

Details

• Both where: tables → @MethodSource providers, preserving the 10<<10/100<<10 shift intent (not flattened to decimals).
• V0.4's metaStruct verifier closure → a @FunctionalInterface MetaStructVerifier<E>.
• The format-agnostic decode helpers — assertEqualsWithNullAsEmpty, the metrics unpackNumber switch, and the growable capturing WritableByteChannel — are extracted to a shared PayloadVerifiers helper reused by both tests. The two PayloadVerifiers themselves stay per-test because V0.4 (inline strings) and V0.5 (dictionary-compressed string indices) decode different wire formats.

Two behaviors that DDSpecification / Groovy provided implicitly are now explicit:

1. Numeric metrics are compared via longValue(). Groovy's dynamic dispatch routed assertEquals(Long, Integer) to the primitive assertEquals(long, long) overload (numeric equality); Java's static overload resolution would pick the Object overload and compare by reference type, which fails once msgpack's minimal encoding narrows a Long thread id back to an Integer.
2. ProcessTags lifecycle: the ProcessTags static is re-synced to the per-test Config via @ExtendWith(WithConfigExtension.class) + a @BeforeEach, and the body-overflow test disables process tags with @WithConfig (so the dictionary-size calculation stays stable).

Testing

Test count is unchanged: V0.4 = 23, V0.5 = 30 (53 total), all green. Verified the original Groovy suite passes in the same environment before porting.

🤖 Generated with Claude Code

[dd-octo-sts]

🟡 Java Benchmark SLOs — Performance SLO warning (near threshold)

Suite	Status
Startup	🟡 warning

SLO thresholds are defined here based on automatically generated metrics. A warning is raised when results are within 5% of the threshold.

PR vs. master results

Scenario	Candidate	master	Δ (95% CI of mean)
startup:insecure-bank:iast:Agent	13.96 s	13.93 s	[-0.5%; +1.0%] (no difference)
startup:insecure-bank:tracing:Agent	12.87 s	12.95 s	[-1.5%; +0.2%] (no difference)
startup:petclinic:appsec:Agent	17.03 s	16.87 s	[-5.2%; +7.0%] (unstable)
startup:petclinic:iast:Agent	16.86 s	17.02 s	[-7.0%; +5.1%] (unstable)
startup:petclinic:profiling:Agent	17.34 s	17.39 s	[-2.3%; +1.6%] (no difference)
startup:petclinic:sca:Agent	17.44 s	17.03 s	[-2.1%; +6.9%] (no difference)
startup:petclinic:tracing:Agent	16.45 s	16.29 s	[-3.3%; +5.3%] (no difference)

Commit: 4e2187f8 · CI Pipeline · Benchmarking Platform UI

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Load and DaCapo benchmarks can be triggered manually in the GitLab pipeline. Results will appear in the Benchmarking Platform UI after completion.