diff --git a/build-common/test/org/jetbrains/kotlin/incremental/testingUtils/classFilesComparison.kt b/build-common/test/org/jetbrains/kotlin/incremental/testingUtils/classFilesComparison.kt
index 3259d6a5529..b4f4a470bfa 100644
--- a/build-common/test/org/jetbrains/kotlin/incremental/testingUtils/classFilesComparison.kt
+++ b/build-common/test/org/jetbrains/kotlin/incremental/testingUtils/classFilesComparison.kt
@@ -17,7 +17,11 @@
 package org.jetbrains.kotlin.incremental.testingUtils
 
 import com.intellij.openapi.util.io.FileUtil
+import com.sun.xml.internal.messaging.saaj.util.ByteOutputStream
 import org.jetbrains.kotlin.incremental.LocalFileKotlinClass
+import org.jetbrains.kotlin.js.parser.sourcemaps.SourceMapError
+import org.jetbrains.kotlin.js.parser.sourcemaps.SourceMapParser
+import org.jetbrains.kotlin.js.parser.sourcemaps.SourceMapSuccess
 import org.jetbrains.kotlin.load.kotlin.header.KotlinClassHeader
 import org.jetbrains.kotlin.metadata.DebugProtoBuf
 import org.jetbrains.kotlin.metadata.js.DebugJsProtoBuf
@@ -32,10 +36,7 @@ import org.jetbrains.org.objectweb.asm.ClassReader
 import org.jetbrains.org.objectweb.asm.util.TraceClassVisitor
 import org.junit.Assert
 import org.junit.Assert.assertNotNull
-import java.io.ByteArrayInputStream
-import java.io.File
-import java.io.PrintWriter
-import java.io.StringWriter
+import java.io.*
 import java.util.*
 import java.util.zip.CRC32
 import java.util.zip.GZIPInputStream
@@ -186,6 +187,22 @@ private fun metaJsToString(metaJsFile: File): String {
     return out.toString()
 }
 
+private fun sourceMapFileToString(sourceMapFile: File, generatedJsFile: File): String {
+    val sourceMapParseResult = SourceMapParser.parse(StringReader(sourceMapFile.readText()))
+    return when (sourceMapParseResult) {
+        is SourceMapSuccess -> {
+            val bytesOut = ByteArrayOutputStream()
+            PrintStream(bytesOut).use { printStream ->
+                sourceMapParseResult.value.debugVerbose(printStream, generatedJsFile)
+            }
+            bytesOut.toString()
+        }
+        is SourceMapError -> {
+            sourceMapParseResult.message
+        }
+    }
+}
+
 private fun getExtensionRegistry(): ExtensionRegistry {
     val registry = ExtensionRegistry.newInstance()!!
     DebugJvmProtoBuf.registerAllExtensions(registry)
@@ -200,6 +217,10 @@ private fun fileToStringRepresentation(file: File): String {
         file.name.endsWith(KotlinJavascriptMetadataUtils.META_JS_SUFFIX) -> {
             metaJsToString(file)
         }
+        file.name.endsWith(".js.map") -> {
+            val generatedJsPath = file.canonicalPath.removeSuffix(".map")
+            sourceMapFileToString(file, File(generatedJsPath))
+        }
         else -> {
             file.readText()
         }
diff --git a/js/js.parser/src/org/jetbrains/kotlin/js/parser/sourcemaps/SourceMap.kt b/js/js.parser/src/org/jetbrains/kotlin/js/parser/sourcemaps/SourceMap.kt
index 83c3f697771..95c06fd1dab 100644
--- a/js/js.parser/src/org/jetbrains/kotlin/js/parser/sourcemaps/SourceMap.kt
+++ b/js/js.parser/src/org/jetbrains/kotlin/js/parser/sourcemaps/SourceMap.kt
@@ -16,6 +16,7 @@
 
 package org.jetbrains.kotlin.js.parser.sourcemaps
 
+import java.io.File
 import java.io.PrintStream
 import java.io.Reader
 
@@ -31,13 +32,30 @@ class SourceMap(val sourceContentResolver: (String) -> Reader?) {
             writer.println()
         }
     }
+
+    fun debugVerbose(writer: PrintStream, generatedJsFile: File) {
+        assert(generatedJsFile.exists()) { "$generatedJsFile does not exist!" }
+        val generatedLines = generatedJsFile.readLines().toTypedArray()
+        for ((index, group) in groups.withIndex()) {
+            writer.print("${index + 1}:")
+            val generatedLine = generatedLines[index]
+            val segmentsByColumn = group.segments.map { it.generatedColumnNumber to it }.toMap()
+            for (i in generatedLine.indices) {
+                segmentsByColumn[i]?.let { (_, sourceFile, sourceLine, sourceColumn) ->
+                    writer.print("<$sourceFile:${sourceLine + 1}:${sourceColumn + 1}>")
+                }
+                writer.print(generatedLine[i])
+            }
+            writer.println()
+        }
+    }
 }
 
-class SourceMapSegment(
-        val generatedColumnNumber: Int,
-        val sourceFileName: String?,
-        val sourceLineNumber: Int,
-        val sourceColumnNumber: Int
+data class SourceMapSegment(
+    val generatedColumnNumber: Int,
+    val sourceFileName: String?,
+    val sourceLineNumber: Int,
+    val sourceColumnNumber: Int
 )
 
 class SourceMapGroup {