diff --git a/compiler/tests/org/jetbrains/jet/InTextDirectivesUtils.java b/compiler/tests/org/jetbrains/jet/InTextDirectivesUtils.java
index 3ad7b5b4f30..e29904fb0c6 100644
--- a/compiler/tests/org/jetbrains/jet/InTextDirectivesUtils.java
+++ b/compiler/tests/org/jetbrains/jet/InTextDirectivesUtils.java
@@ -16,17 +16,18 @@
 
 package org.jetbrains.jet;
 
+import com.google.common.collect.Lists;
+import com.google.common.collect.Sets;
 import com.intellij.openapi.util.text.StringUtil;
 import com.intellij.util.ArrayUtil;
+import junit.framework.Assert;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 
 import java.io.BufferedReader;
 import java.io.IOException;
 import java.io.StringReader;
-import java.util.ArrayList;
-import java.util.Arrays;
-import java.util.List;
+import java.util.*;
 
 public final class InTextDirectivesUtils {
 
@@ -50,7 +51,7 @@ public final class InTextDirectivesUtils {
 
     @NotNull
     public static List<String> findListWithPrefix(String fileText, String... prefixes) {
-        ArrayList<String> result = new ArrayList<String>();
+        List<String> result = new ArrayList<String>();
 
         for (String line : findLinesWithPrefixRemoved(fileText, prefixes)) {
             String[] variants = line.split(",");
@@ -76,14 +77,17 @@ public final class InTextDirectivesUtils {
 
     @NotNull
     public static List<String> findLinesWithPrefixRemoved(String fileText, String... prefixes) {
-        ArrayList<String> result = new ArrayList<String>();
+        List<String> result = new ArrayList<String>();
+        List<String> cleanedPrefixes = cleanDirectivesFromComments(Arrays.asList(prefixes));
 
-        for (String line : fileNonEmptyLines(fileText)) {
-            for (String prefix : prefixes) {
+        for (String line : fileNonEmptyCommentedLines(fileText)) {
+            for (String prefix : cleanedPrefixes) {
                 if (line.startsWith(prefix)) {
                     String noPrefixLine = line.substring(prefix.length());
 
-                    if (noPrefixLine.isEmpty() || Character.isWhitespace(noPrefixLine.charAt(0))) {
+                    if (noPrefixLine.isEmpty() ||
+                            Character.isWhitespace(noPrefixLine.charAt(0)) ||
+                            Character.isWhitespace(prefix.charAt(prefix.length() - 1))) {
                         result.add(noPrefixLine.trim());
                         break;
                     }
@@ -94,9 +98,51 @@ public final class InTextDirectivesUtils {
         return result;
     }
 
+    public static void assertHasUnknownPrefixes(String fileText, Collection<String> knownPrefixes) {
+        Set<String> prefixes = Sets.newHashSet();
+
+        for (String line : fileNonEmptyCommentedLines(fileText)) {
+            String prefix = probableDirective(line);
+            if (prefix != null) {
+                prefixes.add(prefix);
+            }
+        }
+
+        prefixes.removeAll(cleanDirectivesFromComments(knownPrefixes));
+
+        Assert.assertTrue("File contains some unexpected directives" + prefixes, prefixes.isEmpty());
+    }
+
+    private static String probableDirective(String line) {
+        String[] arr = line.split(" ", 2);
+        String firstWord = arr[0];
+
+        if (firstWord.length() > 1 && StringUtil.toUpperCase(firstWord).equals(firstWord)) {
+            return firstWord;
+        }
+
+        return null;
+    }
+
+    private static List<String> cleanDirectivesFromComments(Collection<String> prefixes) {
+        List<String> resultPrefixes = Lists.newArrayList();
+
+        for (String prefix : prefixes) {
+            if (prefix.startsWith("//")) {
+                resultPrefixes.add(StringUtil.trimLeading(prefix.substring(2)));
+            }
+            else {
+                resultPrefixes.add(prefix);
+            }
+        }
+
+        return resultPrefixes;
+    }
+
+
     @NotNull
-    private static List<String> fileNonEmptyLines(String fileText) {
-        ArrayList<String> result = new ArrayList<String>();
+    private static List<String> fileNonEmptyCommentedLines(String fileText) {
+        List<String> result = new ArrayList<String>();
 
         try {
             BufferedReader reader = new BufferedReader(new StringReader(fileText));
@@ -104,8 +150,11 @@ public final class InTextDirectivesUtils {
                 String line;
 
                 while ((line = reader.readLine()) != null) {
-                    if (!line.isEmpty()) {
-                        result.add(line.trim());
+                    if (line.startsWith("//")) {
+                        String uncommentedLine = line.substring(2).trim();
+                        if (!uncommentedLine.isEmpty()) {
+                            result.add(uncommentedLine);
+                        }
                     }
                 }
             } finally {