diff --git a/compiler/fir/resolve/tests/org/jetbrains/kotlin/fir/AbstractFirOldFrontendDiagnosticsTest.kt b/compiler/fir/resolve/tests/org/jetbrains/kotlin/fir/AbstractFirOldFrontendDiagnosticsTest.kt
index fbf49de1de0..e22c1d6747e 100644
--- a/compiler/fir/resolve/tests/org/jetbrains/kotlin/fir/AbstractFirOldFrontendDiagnosticsTest.kt
+++ b/compiler/fir/resolve/tests/org/jetbrains/kotlin/fir/AbstractFirOldFrontendDiagnosticsTest.kt
@@ -11,14 +11,6 @@ import org.jetbrains.kotlin.test.KotlinTestUtils
 import java.io.File
 
 abstract class AbstractFirOldFrontendDiagnosticsTest : AbstractFirDiagnosticsTest() {
-    companion object {
-        private val DIAGNOSTIC_PATTERN = Regex("(<!>|(<!(.(\".*\")*?)+?!>))")
-
-        private fun loadTestDataWithoutDiagnostics(file: File): String {
-            return KotlinTestUtils.doLoadFile(file).replace(DIAGNOSTIC_PATTERN, "")
-        }
-    }
-
     override fun createTestFileFromPath(filePath: String): File {
         val newPath = filePath.replace(".kt", ".fir.kt")
         return File(newPath).also {
diff --git a/compiler/tests-common/tests/org/jetbrains/kotlin/checkers/AbstractDiagnosticsTest.kt b/compiler/tests-common/tests/org/jetbrains/kotlin/checkers/AbstractDiagnosticsTest.kt
index b9275087caa..dcf01861180 100644
--- a/compiler/tests-common/tests/org/jetbrains/kotlin/checkers/AbstractDiagnosticsTest.kt
+++ b/compiler/tests-common/tests/org/jetbrains/kotlin/checkers/AbstractDiagnosticsTest.kt
@@ -214,6 +214,16 @@ abstract class AbstractDiagnosticsTest : BaseDiagnosticsTest() {
         performAdditionalChecksAfterDiagnostics(
             testDataFile, files, groupedByModule, modules, moduleBindings, languageVersionSettingsByModule
         )
+        checkOriginalAndFirTestdataIdentity(testDataFile)
+    }
+
+    private fun checkOriginalAndFirTestdataIdentity(testDataFile: File) {
+        val firTestDataFile = File(testDataFile.absolutePath.replace(".kt", ".fir.kt"))
+        if (!firTestDataFile.exists()) return
+        val originalTestData = loadTestDataWithoutDiagnostics(testDataFile)
+        val firTestData = loadTestDataWithoutDiagnostics(firTestDataFile)
+        val message = "Original and fir test data doesn't identical. Please, add changes from ${testDataFile.name} to ${firTestDataFile.name}"
+        TestCase.assertEquals(message, originalTestData, firTestData)
     }
 
     private fun StringBuilder.cleanupInferenceDiagnostics(): String = replace(Regex("NI;([\\S]*), OI;\\1([,!])")) { it.groupValues[1] + it.groupValues[2] }
diff --git a/compiler/tests-common/tests/org/jetbrains/kotlin/checkers/BaseDiagnosticsTest.kt b/compiler/tests-common/tests/org/jetbrains/kotlin/checkers/BaseDiagnosticsTest.kt
index 9d7c21aa8f4..d1e1373ce43 100644
--- a/compiler/tests-common/tests/org/jetbrains/kotlin/checkers/BaseDiagnosticsTest.kt
+++ b/compiler/tests-common/tests/org/jetbrains/kotlin/checkers/BaseDiagnosticsTest.kt
@@ -475,6 +475,12 @@ abstract class BaseDiagnosticsTest : KotlinMultiFileTestWithJava<TestModule, Tes
                 Condition { diagnostic -> diagnostic.factory in DIAGNOSTICS_TO_INCLUDE_ANYWAY }
             )
         }
+
+        private val DIAGNOSTIC_IN_TESTDATA_PATTERN = Regex("(<!>|(<!(.(\".*\")*?)+?!>))")
+
+        fun loadTestDataWithoutDiagnostics(file: File): String {
+            return KotlinTestUtils.doLoadFile(file).replace(DIAGNOSTIC_IN_TESTDATA_PATTERN, "")
+        }
     }
 
     private fun parseJvmTarget(directiveMap: Map<String, String>) = directiveMap[JVM_TARGET]?.let { JvmTarget.fromString(it) }