fix(smoke-tests): share debugger test helpers via java-test-fixtures

Gradle 9.5 added a `DependencyHandler.project(String)` overload that
returns a `ProjectDependency`. Inside a `dependencies { }` block, that
overload now shadows the `Project.project(String)` accessor that
previously resolved via Groovy fallback. Result:
`project(':foo').sourceSets` no longer reaches the producing project's
source sets — it hits a `DefaultProjectDependency` and fails with
"unknown property 'sourceSets'".

`dd-smoke-tests/debugger-integration-tests/build.gradle:21` used
`project(':dd-java-agent:agent-debugger').sourceSets.test.output` to
pull two helper classes (`LogProbeTestHelper`, `MoshiSnapshotTestHelper`)
from `agent-debugger`'s test sources.

Apply the canonical Gradle 9.5 fix (see #11367): expose the helpers via
the `java-test-fixtures` plugin on `agent-debugger`. The helpers move
from `src/test/java/com/datadog/debugger/util/` to
`src/testFixtures/java/com/datadog/debugger/util/` (same package), and
the consumer pulls them in via
`testImplementation testFixtures(project(':dd-java-agent:agent-debugger'))`.

The 15 existing in-project consumers (test classes inside agent-debugger)
keep working because the testFixtures source set is automatically on the
`test` source set's classpath.

This unblocks running the root build on Gradle 9.5.1.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: bric3

dd-java-agent/agent-debugger/build.gradle

@@ -3,6 +3,7 @@ import com.github.jengelman.gradle.plugins.shadow.tasks.ShadowJar
 plugins {
   id 'com.gradleup.shadow'
   id 'dd-trace-java.version-file'
+  id 'java-test-fixtures'
 }
 
 apply from: "$rootDir/gradle/java.gradle"
@@ -47,6 +48,14 @@ dependencies {
   implementation libs.okhttp
   implementation libs.slf4j
 
+  // Dependencies needed to compile the test-fixture helpers (LogProbeTestHelper,
+  // MoshiSnapshotTestHelper); they reference siblings + Moshi + internal-api.
+  testFixturesImplementation project(':dd-java-agent:agent-debugger:debugger-bootstrap')
+  testFixturesImplementation project(':dd-java-agent:agent-debugger:debugger-el')
+  testFixturesImplementation project(':internal-api')
+  testFixturesImplementation libs.moshi
+  testFixturesImplementation libs.junit.jupiter
+
   testImplementation libs.asm.util
   testImplementation libs.bundles.junit5
   testImplementation libs.junit.jupiter.params

…og/debugger/util/LogProbeTestHelper.java …og/debugger/util/LogProbeTestHelper.javadd-java-agent/agent-debugger/src/test/java/com/datadog/debugger/util/LogProbeTestHelper.java renamed to dd-java-agent/agent-debugger/src/testFixtures/java/com/datadog/debugger/util/LogProbeTestHelper.java dd-java-agent/agent-debugger/src/test/java/com/datadog/debugger/util/LogProbeTestHelper.java renamed to dd-java-agent/agent-debugger/src/testFixtures/java/com/datadog/debugger/util/LogProbeTestHelper.java

@@ -17,8 +17,8 @@ dependencies {
   testImplementation project(':dd-java-agent:agent-debugger')
   testImplementation project(':dd-java-agent:agent-debugger:debugger-el')
   testImplementation project(':dd-java-agent:agent-debugger:debugger-bootstrap')
-  // dependency on some helper classes made only for tests
-  testImplementation project(':dd-java-agent:agent-debugger').sourceSets.test.output
+  // helper classes shared via java-test-fixtures (LogProbeTestHelper, MoshiSnapshotTestHelper)
+  testImplementation testFixtures(project(':dd-java-agent:agent-debugger'))
   testImplementation libs.bundles.junit5
   testImplementation libs.bundles.mockito
 }