diff --git a/compiler/testData/diagnostics/tests/j+k/Simple.jet b/compiler/testData/diagnostics/tests/j+k/Simple.jet
new file mode 100644
index 00000000000..322ff1fa99b
--- /dev/null
+++ b/compiler/testData/diagnostics/tests/j+k/Simple.jet
@@ -0,0 +1,9 @@
+// FILE: A.java
+
+class A {
+    void f() { }
+}
+
+// FILE: B.kt
+
+fun foo(a: A) = a.f()
diff --git a/compiler/tests/org/jetbrains/jet/checkers/JetDiagnosticsTest.java b/compiler/tests/org/jetbrains/jet/checkers/JetDiagnosticsTest.java
index f4716276339..510a28049e2 100644
--- a/compiler/tests/org/jetbrains/jet/checkers/JetDiagnosticsTest.java
+++ b/compiler/tests/org/jetbrains/jet/checkers/JetDiagnosticsTest.java
@@ -18,8 +18,16 @@ package org.jetbrains.jet.checkers;
 
 import com.google.common.base.Predicates;
 import com.google.common.collect.Lists;
+import com.google.common.io.ByteStreams;
+import com.google.common.io.CharStreams;
+import com.google.common.io.Files;
+import com.intellij.lang.java.JavaLanguage;
 import com.intellij.openapi.util.TextRange;
+import com.intellij.openapi.util.io.FileUtil;
+import com.intellij.psi.PsiElementVisitor;
+import com.intellij.psi.PsiErrorElement;
 import com.intellij.psi.PsiFile;
+import com.intellij.psi.PsiFileFactory;
 import junit.framework.Test;
 import org.jetbrains.annotations.NonNls;
 import org.jetbrains.annotations.NotNull;
@@ -35,6 +43,8 @@ import org.jetbrains.jet.lang.resolve.BindingContext;
 import org.jetbrains.jet.lang.resolve.java.AnalyzerFacade;
 
 import java.io.File;
+import java.io.IOException;
+import java.nio.charset.Charset;
 import java.util.List;
 
 /**
@@ -59,17 +69,32 @@ public class JetDiagnosticsTest extends JetLiteFixture {
         private final String expectedText;
         private final String clearText;
         private final JetFile jetFile;
+        private final PsiFile javaFile;
 
         public TestFile(String fileName, String textWithMarkers) {
-            expectedText = textWithMarkers;
-            clearText = CheckerTestUtil.parseDiagnosedRanges(expectedText, diagnosedRanges);
-            jetFile = createCheckAndReturnPsiFile(fileName, clearText);
-            for (CheckerTestUtil.DiagnosedRange diagnosedRange : diagnosedRanges) {
-                diagnosedRange.setFile(jetFile);
+            if (fileName.endsWith(".java")) {
+                this.javaFile = PsiFileFactory.getInstance(getProject()).createFileFromText(fileName, JavaLanguage.INSTANCE, textWithMarkers);
+                // TODO: check there's not syntax errors
+                this.jetFile = null;
+                this.expectedText = this.clearText = textWithMarkers;
+            } else {
+                expectedText = textWithMarkers;
+                clearText = CheckerTestUtil.parseDiagnosedRanges(expectedText, diagnosedRanges);
+                this.javaFile = null;
+                this.jetFile = createCheckAndReturnPsiFile(fileName, clearText);
+                for (CheckerTestUtil.DiagnosedRange diagnosedRange : diagnosedRanges) {
+                    diagnosedRange.setFile(jetFile);
+                }
             }
         }
 
         public boolean getActualText(BindingContext bindingContext, StringBuilder actualText) {
+            if (this.jetFile == null) {
+                // TODO: check java files too
+                actualText.append(this.clearText);
+                return true;
+            }
+
             final boolean ok[] = { true };
             CheckerTestUtil.diagnosticsDiff(diagnosedRanges, CheckerTestUtil.getDiagnosticsIncludingSyntaxErrors(bindingContext, jetFile), new CheckerTestUtil.DiagnosticDiffCallbacks() {
                 @NotNull
@@ -99,8 +124,24 @@ public class JetDiagnosticsTest extends JetLiteFixture {
 
     }
 
+    private boolean hasJavaFiles;
+    private File javaFilesDir;
+
+    private void writeJavaFile(@NotNull String fileName, @NotNull String content) {
+        try {
+            File javaFile = new File(javaFilesDir, fileName);
+            JetTestUtils.mkdirs(javaFile.getParentFile());
+            Files.write(content, javaFile, Charset.forName("utf-8"));
+            hasJavaFiles = true;
+        } catch (Exception e) {
+            throw new RuntimeException(e);
+        }
+    }
+
     @Override
     public void runTest() throws Exception {
+        javaFilesDir = new File(FileUtil.getTempDirectory(), "java-files");
+
         String testFileName = name + ".jet";
 
         String expectedText = loadFile(testFileName);
@@ -108,16 +149,26 @@ public class JetDiagnosticsTest extends JetLiteFixture {
         List<TestFile> testFileFiles = JetTestUtils.createTestFiles(testFileName, expectedText, new JetTestUtils.TestFileFactory<TestFile>() {
             @Override
             public TestFile create(String fileName, String text) {
+                if (fileName.endsWith(".java")) {
+                    writeJavaFile(fileName, text);
+                }
                 return new TestFile(fileName, text);
             }
         });
 
         boolean importJdk = expectedText.contains("+JDK");
 //        Configuration configuration = importJdk ? JavaBridgeConfiguration.createJavaBridgeConfiguration(getProject()) : Configuration.EMPTY;
+        if (hasJavaFiles) {
+            // According to yole@ the only way to import java files is to write them on disk
+            // -- stepan.koltsov@ 2012-02-29
+            myEnvironment.addToClasspath(javaFilesDir);
+        }
 
         List<JetFile> jetFiles = Lists.newArrayList();
         for (TestFile testFileFile : testFileFiles) {
-            jetFiles.add(testFileFile.jetFile);
+            if (testFileFile.jetFile != null) {
+                jetFiles.add(testFileFile.jetFile);
+            }
         }
 
         BindingContext bindingContext;