diff --git a/generators/src/org/jetbrains/jet/generators/tests/generateTestDataForReservedWords.kt b/generators/src/org/jetbrains/jet/generators/tests/generateTestDataForReservedWords.kt
index 596806c32fa..042911b2b74 100644
--- a/generators/src/org/jetbrains/jet/generators/tests/generateTestDataForReservedWords.kt
+++ b/generators/src/org/jetbrains/jet/generators/tests/generateTestDataForReservedWords.kt
@@ -39,8 +39,10 @@ fun main(args: Array<String>) {
     generateTestDataForReservedWords()
 }
 
+val TEST_DATA_DIR_FOR_RESERVED_WORDS = "js/js.translator/testData/reservedWords/cases"
+
 fun generateTestDataForReservedWords() {
-    generate("js/js.translator/testData/reservedWords/cases") {
+    generate(TEST_DATA_DIR_FOR_RESERVED_WORDS) {
         suite("toplevel",
 """
 $DEFINITION_MARKER
@@ -239,10 +241,29 @@ class TestDataBuilder() {
     }
 
     fun generate(testDataDirPath: String) {
+
+        fun File.readLinesOrNull() = if (!exists()) null else readLines()
+
         val testDataDir = File(testDataDirPath)
+
+        val shouldBeEscapedFile = File("$testDataDirPath/SHOULD_BE_ESCAPED.txt")
+        val shouldNotBeEscapedFile = File("$testDataDirPath/SHOULD_NOT_BE_ESCAPED.txt")
+
+        val shouldBeEscapedFromFile = shouldBeEscapedFile.readLinesOrNull()?.drop(1)
+        val shouldNotBeEscapedFromFile = shouldNotBeEscapedFile.readLinesOrNull()?.drop(1)
+
+        val isCreatingFromScratch = shouldBeEscapedFromFile != SHOULD_BE_ESCAPED || shouldNotBeEscapedFromFile != SHOULD_NOT_BE_ESCAPED
+
         if (!testDataDir.exists() && !testDataDir.mkdirs()) {
-            println("Unable to find or create test data dir: '$testDataDirPath'.")
-            return
+            error("Unable to find or create test data directory: '$testDataDirPath'.")
+        }
+        else if (isCreatingFromScratch) {
+            if (testDataDir.listFiles()?.all { it.delete() } ?: true) {
+                println("Create testdata files from scratch.")
+            }
+            else {
+                error("Can not clean testdata directory.")
+            }
         }
 
         for (suite in suites) {
@@ -264,10 +285,19 @@ class TestDataBuilder() {
 
                     val fileName = "${suite.name.decapitalize()}${case.name.capitalize()}${keyword.capitalize()}.kt"
 
-                    File(testDataDirPath + "/" + fileName).writeText(out)
+                    val testDataFile = File(testDataDirPath + "/" + fileName)
+
+                    assert(isCreatingFromScratch xor testDataFile.exists(), "Unexpected file name: $fileName")
+
+                    testDataFile.writeText(out)
                 }
             }
         }
+
+        if (isCreatingFromScratch) {
+            shouldBeEscapedFile.writeText("$PREAMBLE_MESSAGE\n${SHOULD_BE_ESCAPED.join("\n")}")
+            shouldNotBeEscapedFile.writeText("$PREAMBLE_MESSAGE\n${SHOULD_NOT_BE_ESCAPED.join("\n")}")
+        }
     }
 }
 
@@ -283,9 +313,10 @@ val DECLARATION_INIT_MARKER = "DECLARATION_INIT"
 val TEST_BLOCK_MARKER = "TEST_BLOCK"
 val KEYWORD_MARKER = "KEYWORD"
 
+val PREAMBLE_MESSAGE = "NOTE THIS FILE IS AUTO-GENERATED by the generateTestDataForReservedWords.kt. DO NOT EDIT!"
 val PREAMBLE = """package foo
 
-// NOTE THIS FILE IS AUTO-GENERATED by the generateTestDataForReservedWords.kt. DO NOT EDIT!
+// $PREAMBLE_MESSAGE
 """
 
 fun testRenamed(reference: String = "$KEYWORD_MARKER") = "testRenamed(\"$KEYWORD_MARKER\", { $reference })"
@@ -299,11 +330,8 @@ val testNotRenamedByRef = testNotRenamed("::$KEYWORD_MARKER")
 
 // KEYWORDS
 
-val ALL_KEYWORDS = JsFunctionScope.RESERVED_WORDS.toList()
-
-val SHOULD_BE_ESCAPED = (ALL_KEYWORDS.filter { it in KeywordStringsGenerated.KEYWORDS } union setOf("catch", "finally")).toSortedList()
-val SHOULD_NOT_BE_ESCAPED = ALL_KEYWORDS.filter { it !in SHOULD_BE_ESCAPED }.toSortedList()
-
+val SHOULD_BE_ESCAPED = JsFunctionScope.RESERVED_WORDS.filter { it in KeywordStringsGenerated.KEYWORDS }.toSortedList()
+val SHOULD_NOT_BE_ESCAPED = JsFunctionScope.RESERVED_WORDS.filter { it !in SHOULD_BE_ESCAPED }.toSortedList()
 
 // all keywords by portions
 
@@ -321,11 +349,14 @@ fun <T> List<T>.cyclicStream() = CyclicStream(this)
 
 class CyclicStream<T>(val c: List<T>) : Stream<T> {
     var i = 0
-    override fun iterator(): Iterator<T> = object : Iterator<T>{
+
+    val iterator = object : Iterator<T> {
         override fun next(): T {
-            i = if (i >= c.size) 0 else i
+            i = if (i >= c.size()) 0 else i
             return c[i++]
         }
         override fun hasNext(): Boolean = true
     }
+
+    override fun iterator(): Iterator<T> = iterator
 }
\ No newline at end of file