diff --git a/teavm-classlib/src/main/java/org/teavm/classlibgen/ClasslibTestGenerator.java b/teavm-classlib/src/main/java/org/teavm/classlibgen/ClasslibTestGenerator.java
index 0c805e994..ecedd8f31 100644
--- a/teavm-classlib/src/main/java/org/teavm/classlibgen/ClasslibTestGenerator.java
+++ b/teavm-classlib/src/main/java/org/teavm/classlibgen/ClasslibTestGenerator.java
@@ -1,9 +1,6 @@
 package org.teavm.classlibgen;
 
-import java.io.FileOutputStream;
-import java.io.IOException;
-import java.io.InputStream;
-import java.io.PrintStream;
+import java.io.*;
 import java.util.*;
 import org.apache.commons.io.IOUtils;
 import org.teavm.codegen.*;
@@ -20,7 +17,7 @@ import org.teavm.optimization.ClassSetOptimizer;
  * @author Alexey Andreev <konsoletyper@gmail.com>
  */
 public class ClasslibTestGenerator {
-    private static PrintStream out;
+    private static File outputDir;
     private static ClasspathClassHolderSource classSource;
     private static Decompiler decompiler;
     private static AliasProvider aliasProvider;
@@ -34,11 +31,28 @@ public class ClasslibTestGenerator {
             "java.lang.VMTests" };
 
     public static void main(String[] args) throws IOException {
-        out = System.out;
-        if (args.length > 0) {
-            out = new PrintStream(new FileOutputStream(args[0]));
-        }
+        outputDir = new File(args[0]);
+        outputDir.mkdirs();
+        resourceToFile("org/teavm/javascript/runtime.js", "runtime.js");
+        resourceToFile("org/teavm/classlib/junit-support.js", "junit-support.js");
+        resourceToFile("org/teavm/classlib/junit.css", "junit.css");
         classSource = new ClasspathClassHolderSource();
+        for (int i = 0; i < testClasses.length; ++i) {
+            testClasses[i] = "org.teavm.classlib." + testClasses[i];
+        }
+        for (String testClass : testClasses) {
+            ClassHolder classHolder = classSource.getClassHolder(testClass);
+            findTests(classHolder);
+        }
+        writer.append("runTests = function() {").newLine().indent();
+        writer.append("document.getElementById(\"start-button\").style.display = 'none';").newLine();
+        for (String testClass : testClasses) {
+            renderClassTest(classSource.getClassHolder(testClass));
+        }
+        writer.outdent().append("}").newLine();
+    }
+
+    private static void decompileClassesForTest(MethodReference methodRef, String targetName) throws IOException {
         decompiler = new Decompiler(classSource);
         aliasProvider = new MinifyingAliasProvider();
         naming = new DefaultNamingStrategy(aliasProvider, classSource);
@@ -47,41 +61,21 @@ public class ClasslibTestGenerator {
         builder.setMinified(true);
         writer = builder.build();
         renderer = new Renderer(writer, classSource);
+        renderer.renderRuntime();
         DependencyChecker dependencyChecker = new DependencyChecker(classSource);
-        for (int i = 0; i < testClasses.length; ++i) {
-            testClasses[i] = "org.teavm.classlib." + testClasses[i];
-        }
-        for (String testClass : testClasses) {
-            ClassHolder classHolder = classSource.getClassHolder(testClass);
-            findTests(classHolder);
-            MethodReference cons = new MethodReference(testClass, new MethodDescriptor("<init>", ValueType.VOID));
-            dependencyChecker.addEntryPoint(cons);
-        }
-        for (MethodReference methodRef : testMethods) {
-            dependencyChecker.addEntryPoint(methodRef);
-        }
+        MethodReference cons = new MethodReference(methodRef.getClassName(),
+                new MethodDescriptor("<init>", ValueType.VOID));
+        dependencyChecker.addEntryPoint(cons);
+        dependencyChecker.addEntryPoint(methodRef);
         dependencyChecker.checkDependencies();
         ListableClassHolderSource classSet = dependencyChecker.cutUnachievableClasses();
         ClassSetOptimizer optimizer = new ClassSetOptimizer();
         optimizer.optimizeAll(classSet);
-        decompileClasses(classSet.getClassNames());
-        renderHead();
-        ClassLoader classLoader = ClasslibTestGenerator.class.getClassLoader();
-        try (InputStream input = classLoader.getResourceAsStream("org/teavm/classlib/junit-support.js")) {
-            out.println(IOUtils.toString(input));
-        }
-        try (InputStream input = classLoader.getResourceAsStream("org/teavm/javascript/runtime.js")) {
-            out.println(IOUtils.toString(input));
-        }
         renderer.renderRuntime();
-        writer.append("runTests = function() {").newLine().indent();
-        writer.append("document.getElementById(\"start-button\").style.display = 'none';").newLine();
-        for (String testClass : testClasses) {
-            renderClassTest(classSource.getClassHolder(testClass));
+        decompileClasses(classSet.getClassNames());
+        try (Writer out = new OutputStreamWriter(new FileOutputStream(new File(outputDir, targetName)), "UTF-8")) {
+            out.write(writer.toString());
         }
-        writer.outdent().append("}").newLine();
-        out.println(writer);
-        renderFoot();
     }
 
     private static void decompileClasses(Collection<String> classNames) {
@@ -91,39 +85,6 @@ public class ClasslibTestGenerator {
         }
     }
 
-    private static void renderHead() {
-        out.println("<!DOCTYPE html>");
-        out.println("<html>");
-        out.println("  <head>");
-        out.println("    <title>TeaVM JUnit tests</title>");
-        out.println("    <meta http-equiv=\"Content-Type\" content=\"text/html;charset=UTF-8\"/>");
-        out.println("    <title>TeaVM JUnit tests</title>");
-        out.println("    <style type=\"text/css\">");
-        out.println("       table {");
-        out.println("           border-collapse: collapse;");
-        out.println("           border: 2px solid black;");
-        out.println("           margin: 2em 1em 2em 1em;");
-        out.println("       }");
-        out.println("       table td, table th {");
-        out.println("           border: 1px solid gray;");
-        out.println("           padding: 0.1em 0.5em 0.2em 0.5em;");
-        out.println("       }");
-        out.println("       table thead, table tfoot {");
-        out.println("           border: 2px solid black;");
-        out.println("       }");
-        out.println("    </style>");
-        out.println("  </head>");
-        out.println("  <body>");
-        out.println("    <script type=\"text/javascript\">");
-    }
-
-    private static void renderFoot() {
-        out.println("    </script>");
-        out.println("    <button id=\"start-button\" onclick=\"runTests()\">Run tests</button>");
-        out.println("  </body>");
-        out.println("</html>");
-    }
-
     private static void renderClassTest(ClassHolder cls) {
         List<MethodReference> methods = groupedMethods.get(cls.getName());
         writer.append("testClass(\"" + cls.getName() + "\", function() {").newLine().indent();
@@ -159,4 +120,12 @@ public class ClasslibTestGenerator {
             }
         }
     }
+
+    private static void resourceToFile(String resource, String fileName) throws IOException {
+        try (InputStream input = ClasslibTestGenerator.class.getClassLoader().getResourceAsStream(resource)) {
+            try (OutputStream output = new FileOutputStream(new File(outputDir, fileName))) {
+                IOUtils.copy(input, output);
+            }
+        }
+    }
 }
diff --git a/teavm-classlib/src/main/resources/org/teavm/classlib/junit-support.js b/teavm-classlib/src/main/resources/org/teavm/classlib/junit-support.js
index a85f34919..b155cb754 100644
--- a/teavm-classlib/src/main/resources/org/teavm/classlib/junit-support.js
+++ b/teavm-classlib/src/main/resources/org/teavm/classlib/junit-support.js
@@ -1,114 +1,135 @@
-currentTestReportBody = null;
-currentTimeSpent = 0;
-totalTimeSpent = 0;
-currentMethodCount = 0;
-currentStatusCell = null;
-currentExceptionCell = null;
-currentTimeCell = null;
-currentStartTime = 0;
-currentExpectedExceptions = [];
-currentFrame = null;
-
-window.addEventListener("message", function(event) {
-    endTime = new Date().getTime();
-    var message = JSON.parse(event.data);
-    if (message.status == "ok") {
-        if (currentExpectedExceptions.length > 0) {
-            currentStatusCell.appendChild(document.createTextNode("expected exception not thrown"));
-            currentStatusCell.style.color = 'yellow';
-        } else {
-            currentStatusCell.appendChild(document.createTextNode("ok"));
-            currentStatusCell.style.color = 'green';
-        }
-    } else if (message.status == "exception") {
-        if (isExpectedException(e)) {
-            currentStatusCell.appendChild(document.createTextNode("ok"));
-            currentStatusCell.style.color = 'green';
-        } else {
-            currentStatusCell.appendChild(document.createTextNode("unexpected exception"));
-            var exceptionText = document.createElement("pre");
-            exceptionText.appendChild(document.createTextNode(e.stack));
-            currentExceptionCell.appendChild(exceptionText);
-            currentStatusCell.style.color = 'red';
-        }
-    }
-    ++currentMethodCount;
-    var timeSpent = (endTime - currentStartTime) / 1000;
-    currentTimeSpent += timeSpent;
-    currentTimeCell.appendChild(document.createTextNode(timeSpent.toFixed(3)));
-    document.body.removeChild(currentFrame);
-}, false);
-
-runTestCase = function(methodName, path, expectedExceptions) {
-    var row = document.createElement("tr");
-    currentTestReportBody.appendChild(row);
-    var nameCell = document.createElement("td");
-    row.appendChild(nameCell);
-    nameCell.appendChild(document.createTextNode(methodName));
-    currentStatusCell = document.createElement("td");
-    row.appendChild(currentStatusCell);
-    currentExceptionCell = document.createElement("td");
-    row.appendChild(currentExceptionCell);
-    currentTimeCell = document.createElement("td");
-    row.appendChild(currentTimeCell);
-    currentStartTime = new Date().getTime();
-    currentExpectedExceptions = expectedExceptions;
-    var frame = document.createElement("iframe");
-    cirremtFrame = frame;
-    document.body.appendChild(frame);
-    var frameDoc = frame.contentWindow.document;
-    var frameScript = frameDoc.createElement("script");
-    frameScript.src = path;
-    frameDoc.body.appendChild(frameScript);
-        endTime = new Date().getTime();
-        if (expectedExceptions.length > 0) {
-            statusCell.appendChild(document.createTextNode("expected exception not thrown"));
-            statusCell.style.color = 'yellow';
-        } else {
-            statusCell.appendChild(document.createTextNode("ok"));
-            statusCell.style.color = 'green';
-        }
-    } catch (e) {
-        endTime = new Date().getTime();
-        if (isExpectedException(e, expectedExceptions)) {
-            statusCell.appendChild(document.createTextNode("ok"));
-            statusCell.style.color = 'green';
-        } else {
-            statusCell.appendChild(document.createTextNode("unexpected exception"));
-            var exceptionText = document.createElement("pre");
-            exceptionText.appendChild(document.createTextNode(e.stack));
-            exceptionCell.appendChild(exceptionText);
-            statusCell.style.color = 'red';
-        }
-    }
-    ++currentMethodCount;
-    var timeSpent = (endTime - startTime) / 1000;
-    currentTimeSpent += timeSpent;
-    timeCell.appendChild(document.createTextNode(timeSpent.toFixed(3)));
+JUnitServer = function(container) {
+    this.container = container;
+    this.timeSpent = 0;
+    this.totalTimeSpent = 0;
+    this.methodCount = 0;
+    this.statusCell = null;
+    this.exceptionCell = null;
+    this.timeCell = null;
+    this.startTime = 0;
+    this.expectedExceptions = [];
+    this.table = null;
+    this.tableBody = null;
+    this.frame = null;
 }
-
-isExpectedException = function(e) {
-    if (e.javaException !== undefined) {
-        for (var i = 0; i < currentExpectedExceptions.length; ++i) {
-            if (currentExpectedExceptions[i] === e.javaException) {
-                return true;
-            }
+JUnitServer.prototype = new Object();
+JUnitServer.prototype.handleEvent = function(message, callback) {
+    endTime = new Date().getTime();
+    if (message.status === "ok") {
+        if (this.expectedExceptions.length > 0) {
+            this.statusCell.appendChild(document.createTextNode("expected exception not thrown"));
+            this.statusCell.style.color = 'yellow';
+        } else {
+            this.statusCell.appendChild(document.createTextNode("ok"));
+            this.statusCell.style.color = 'green';
+        }
+    } else if (message.status === "exception") {
+        if (message.exception && this.isExpectedException(message.exception)) {
+            this.statusCell.appendChild(document.createTextNode("ok"));
+            this.statusCell.style.color = 'green';
+        } else {
+            this.statusCell.appendChild(document.createTextNode("unexpected exception"));
+            var exceptionText = document.createElement("pre");
+            exceptionText.appendChild(document.createTextNode(message.stack));
+            this.exceptionCell.appendChild(exceptionText);
+            this.statusCell.style.color = 'red';
+        }
+    }
+    ++this.methodCount;
+    var timeSpent = (endTime - this.startTime) / 1000;
+    this.timeSpent += timeSpent;
+    this.timeCell.appendChild(document.createTextNode(timeSpent.toFixed(3)));
+    document.body.removeChild(this.frame);
+    self.frame = null;
+    callback();
+}
+JUnitServer.prototype.isExpectedException = function(ex) {
+    for (var i = 0; i < this.expectedExceptions.length; ++i) {
+        if (this.expectedExceptions[i] === ex) {
+            return true;
         }
     }
     return false;
 }
-
-testClass = function(className, classTests) {
-    currentTimeSpent = 0;
-    currentMethodCount = 0;
-    var table = document.createElement("table");
-    document.body.appendChild(table);
+JUnitServer.prototype.runTestCase = function(methodName, path, expectedExceptions, callback) {
+    this.createRow(methodName);
+    this.startTime = new Date().getTime();
+    this.expectedExceptions = expectedExceptions;
+    var self = this;
+    this.loadCode(path, function() {
+        messageHandler = function(event) {
+            window.removeEventListener("message", messageHandler);
+            self.handleEvent(JSON.parse(event.data), callback);
+        };
+        window.addEventListener("message", messageHandler);
+        self.frame.contentWindow.postMessage("runTest", "*");
+    });
+}
+JUnitServer.prototype.createRow = function(methodName) {
+    var row = document.createElement("tr");
+    this.tableBody.appendChild(row);
+    var nameCell = document.createElement("td");
+    row.appendChild(nameCell);
+    nameCell.appendChild(document.createTextNode(methodName));
+    this.statusCell = document.createElement("td");
+    row.appendChild(this.statusCell);
+    this.exceptionCell = document.createElement("td");
+    row.appendChild(this.exceptionCell);
+    this.timeCell = document.createElement("td");
+    row.appendChild(this.timeCell);
+}
+JUnitServer.prototype.loadCode = function(path, callback) {
+    this.frame = document.createElement("iframe");
+    document.body.appendChild(this.frame);
+    var frameDoc = this.frame.contentWindow.document;
+    var self = this;
+    this.loadScript("junit-support.js", function() {
+        self.loadScript("runtime.js", function() {
+            self.loadScript(path, callback);
+        });
+    });
+}
+JUnitServer.prototype.loadScript = function(name, callback) {
+    var doc = this.frame.contentWindow.document;
+    var script = doc.createElement("script");
+    script.src = name;
+    doc.body.appendChild(script);
+    script.onload = function() {
+        callback();
+    }
+}
+JUnitServer.prototype.runTest = function(test, callback) {
+    this.timeSpent = 0;
+    this.methodCount = 0;
+    this.createTable(test.name);
+    this.runMethodFromList(test.methods, 0, function() {
+        callback();
+    });
+}
+JUnitServer.prototype.runMethodFromList = function(methods, index, callback) {
+    if (index < methods.length) {
+        var method = methods[index];
+        var self = this;
+        this.runTestCase(method.name, method.script, method.expected, function() {
+            self.runMethodFromList(methods, index + 1, callback);
+        });
+    } else {
+        callback();
+    }
+}
+JUnitServer.prototype.createTable = function(name) {
+    this.table = document.createElement("table");
+    this.container.appendChild(this.table);
     var caption = document.createElement("caption");
-    table.appendChild(caption);
-    caption.appendChild(document.createTextNode(className));
-
+    this.table.appendChild(caption);
+    this.createHeader();
+    caption.appendChild(document.createTextNode(name));
+    this.tableBody = document.createElement("tbody");
+    this.table.appendChild(this.tableBody);
+}
+JUnitServer.prototype.createHeader = function() {
     var head = document.createElement("thead");
-    table.appendChild(head);
+    this.table.appendChild(head);
     var headRow = document.createElement("tr");
     head.appendChild(headRow);
     var headCell = document.createElement("th");
@@ -123,14 +144,11 @@ testClass = function(className, classTests) {
     headCell = document.createElement("th");
     headRow.appendChild(headCell);
     headCell.appendChild(document.createTextNode("Time spent, s"));
-
-    var tbody = document.createElement("tbody");
-    table.appendChild(tbody);
-    currentTestReportBody = tbody;
-    classTests();
-
+    this.table.appendChild(head);
+}
+JUnitServer.prototype.createFooter = function() {
     var foot = document.createElement("tfoot");
-    table.appendChild(foot);
+    this.table.appendChild(foot);
     var footRow = document.createElement("tr");
     foot.appendChild(footRow);
     var footName = document.createElement("td");
@@ -138,14 +156,30 @@ testClass = function(className, classTests) {
     footName.appendChild(document.createTextNode("---"));
     var footMethods = document.createElement("td");
     footRow.appendChild(footMethods);
-    footMethods.appendChild(document.createTextNode(currentMethodCount));
+    footMethods.appendChild(document.createTextNode(this.methodCount));
     var footSpace = document.createElement("td");
     footRow.appendChild(footSpace);
     footSpace.appendChild(document.createTextNode("---"));
     var footTime = document.createElement("td");
     footRow.appendChild(footTime);
-    footTime.appendChild(document.createTextNode(currentTimeSpent.toFixed(3)));
-    totalTimeSpent += currentTimeSpent;
+    footTime.appendChild(document.createTextNode(this.timeSpent.toFixed(3)));
+}
 
-    currentTestReportBody = null;
+JUnitClient = {};
+JUnitClient.run = function(runner) {
+    var handler = window.addEventListener("message", function() {
+        window.removeEventListener("message", handler);
+        var message = {};
+        try {
+            runner();
+            message.status = "ok";
+        } catch (e) {
+            message.status = "exception";
+            if (e.$javaException && e.$javaException.$class && e.$javaException.$class.$meta) {
+                message.exception = e.$javaException.$class.$meta.name;
+            }
+            message.stack = e.stack;
+        }
+        window.parent.postMessage(JSON.stringify(message), "*");
+    });
 }
\ No newline at end of file
diff --git a/teavm-classlib/src/main/resources/org/teavm/classlib/junit.html b/teavm-classlib/src/main/resources/org/teavm/classlib/junit.html
index dbd335300..eea39474f 100644
--- a/teavm-classlib/src/main/resources/org/teavm/classlib/junit.html
+++ b/teavm-classlib/src/main/resources/org/teavm/classlib/junit.html
@@ -11,6 +11,7 @@
     <script type="text/javascript">
         function runTests() {
             document.getElementById("start-button").style.display = "none";
+            doRunTests();
         }
     </script>
     <button id="start-button" onclick="runTests()">Run tests</button>