[Infrastructure] Assert dumps don't exist without directive

#KT-58697 Fixed

plugins/kotlinx-serialization/tests/org/jetbrains/kotlinx/serialization/runners/BoxTests.kt

@@ -12,6 +12,7 @@ import org.jetbrains.kotlin.test.runners.codegen.AbstractIrBlackBoxCodegenTest
 import org.jetbrains.kotlinx.serialization.configureForKotlinxSerialization
 import org.jetbrains.kotlin.js.test.ir.AbstractJsIrTest;
 import org.jetbrains.kotlin.test.TargetBackend
+import org.jetbrains.kotlin.test.directives.FirDiagnosticsDirectives
 
 open class AbstractSerializationIrBoxTest : AbstractIrBlackBoxCodegenTest() {
     override fun configure(builder: TestConfigurationBuilder) {
@@ -38,6 +39,16 @@ open class AbstractSerializationFirLightTreeBlackBoxTest : AbstractFirLightTreeB
     override fun configure(builder: TestConfigurationBuilder) {
         super.configure(builder)
         builder.configureForKotlinxSerialization()
+
+        with(builder) {
+            // Necessary because AbstractSerializationFirPsiDiagnosticTest, that runs on the same test data, configures it.
+            // Otherwise, the dump would be automatically deleted.
+            forTestsMatching("*/firMembers/*") {
+                defaultDirectives {
+                    +FirDiagnosticsDirectives.FIR_DUMP
+                }
+            }
+        }
     }
 }