[Gradle] Add integration test for KT-63499

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/kotlin/org/jetbrains/kotlin/gradle/SimpleKotlinGradleIT.kt

@@ -5,13 +5,13 @@ import org.gradle.api.logging.configuration.WarningMode
 import org.gradle.util.GradleVersion
 import org.jetbrains.kotlin.gradle.tasks.KotlinCompilerExecutionStrategy
 import org.jetbrains.kotlin.gradle.testbase.*
+import org.jetbrains.kotlin.gradle.plugin.KotlinSourceSet
 import org.junit.jupiter.api.Disabled
 import org.junit.jupiter.api.DisplayName
 import org.junit.jupiter.api.io.TempDir
 import java.nio.file.Path
 import java.util.zip.ZipFile
 import kotlin.io.path.*
-import kotlin.test.assertEquals
 
 @JvmGradlePluginTests
 @DisplayName("KGP simple tests")
@@ -321,4 +321,28 @@ class SimpleKotlinGradleIT : KGPBaseTest() {
             }
         }
     }
+
+    @Disabled
+    @DisplayName("KT-63499: source sets conventions are not registered since Gradle 8.2")
+    @GradleTestVersions(minVersion = TestVersions.Gradle.G_8_2)
+    @GradleTest
+    fun sourceSetsConventionsAreNotRegistered(gradleVersion: GradleVersion) {
+        project("simpleProject", gradleVersion) {
+            // project's buildscript has to be in Groovy
+            buildGradle.append(
+                //language=Gradle
+                """
+                sourceSets {
+                    main {
+                        customSourceFilesExtensions // try using a property of KotlinSourceSet through the source set convention
+                    }
+                }
+                """.trimIndent()
+            )
+            KotlinSourceSet::customSourceFilesExtensions // ensure the accessed property is available on KotlinSourceSet
+            buildAndFail("help") {
+                assertOutputContains("Could not get unknown property 'customSourceFilesExtensions' for source set 'main' ")
+            }
+        }
+    }
 }