diff --git a/js/js.libraries/src/core/javalang.kt b/js/js.libraries/src/core/javalang.kt
index 379c4999b2f..485a3619260 100644
--- a/js/js.libraries/src/core/javalang.kt
+++ b/js/js.libraries/src/core/javalang.kt
@@ -27,6 +27,9 @@ public class NumberFormatException(message: String? = null) : RuntimeException(m
 @library
 public class NullPointerException(message: String? = null) : RuntimeException(message) {}
 
+@library
+public class AssertionError(message: String? = null) : Error(message) {}
+
 @library
 public interface Runnable {
     public open fun run() : Unit;
diff --git a/js/js.libraries/src/stdlib/testCode.kt b/js/js.libraries/src/stdlib/testCode.kt
index 887bd9e2973..dbdca10fac9 100644
--- a/js/js.libraries/src/stdlib/testCode.kt
+++ b/js/js.libraries/src/stdlib/testCode.kt
@@ -18,14 +18,23 @@ public var asserter: Asserter = QUnitAsserter()
 public class QUnitAsserter(): Asserter {
 
     public override fun assertTrue(lazyMessage: () -> String?, actual: Boolean) {
-        QUnit.ok(actual, lazyMessage())
+        assertTrue(actual, lazyMessage())
     }
 
     public override fun assertTrue(message: String?, actual: Boolean) {
         QUnit.ok(actual, message)
+        if (!actual) failWithMessage(message)
     }
 
-    public override fun fail(message: String?) {
+    public override fun fail(message: String?): Nothing {
         QUnit.ok(false, message)
+        failWithMessage(message)
+    }
+
+    private fun failWithMessage(message: String?): Nothing {
+        if (message == null)
+            throw AssertionError()
+        else
+            throw AssertionError(message)
     }
 }
\ No newline at end of file
diff --git a/js/js.translator/testData/jsTester/jsTester.js b/js/js.translator/testData/jsTester/jsTester.js
index 0b90fb1c61f..660ad3cbae6 100644
--- a/js/js.translator/testData/jsTester/jsTester.js
+++ b/js/js.translator/testData/jsTester/jsTester.js
@@ -21,11 +21,15 @@ var JsTests = (function () {
 
     var assert = function (isTrue, message) {
         if (!isTrue) {
-            reporter.reportError(message);
-            throw failedTest;
+            fail(message);
         }
     };
 
+    var fail = function (message) {
+        reporter.reportError(message);
+        throw failedTest;
+    };
+
     var init = function () {
         init = function() {};
         Kotlin.modules["JS_TESTS"].kotlin.test.init();
@@ -49,6 +53,7 @@ var JsTests = (function () {
     };
     return {
         test: test,
-        assert: assert
+        assert: assert,
+        fail: fail
     }
 })();
diff --git a/js/js.translator/testData/jsTester/jsTester.kt b/js/js.translator/testData/jsTester/jsTester.kt
index badbeaa6c21..b1a46e3f6d6 100644
--- a/js/js.translator/testData/jsTester/jsTester.kt
+++ b/js/js.translator/testData/jsTester/jsTester.kt
@@ -7,10 +7,11 @@ fun init() {
 }
 
 public class JsTestsAsserter() : Asserter {
-    public override fun fail(message: String?) {
-        assert(false, message)
-    }
+    public override fun fail(message: String?): Nothing = failWithMessage(message)
 }
 
 @native("JsTests.assert")
 public fun assert(value: Boolean, message: String?): Unit = noImpl
+
+@native("JsTests.fail")
+private fun failWithMessage(message: String?): Nothing = noImpl
diff --git a/js/js.translator/testData/kotlin_lib.js b/js/js.translator/testData/kotlin_lib.js
index 15e632484ef..627c807ea2f 100644
--- a/js/js.translator/testData/kotlin_lib.js
+++ b/js/js.translator/testData/kotlin_lib.js
@@ -200,6 +200,7 @@
     Kotlin.UnsupportedOperationException = createClassNowWithMessage(Kotlin.RuntimeException);
     Kotlin.IndexOutOfBoundsException = createClassNowWithMessage(Kotlin.RuntimeException);
     Kotlin.IOException = createClassNowWithMessage(Kotlin.Exception);
+    Kotlin.AssertionError = createClassNowWithMessage(Kotlin.Error);
 
     Kotlin.throwNPE = function (message) {
         throw new Kotlin.NullPointerException(message);
diff --git a/libraries/kotlin.test/junit/src/main/kotlin/JUnitSupport.kt b/libraries/kotlin.test/junit/src/main/kotlin/JUnitSupport.kt
index 68e78497a2e..a0aa575d5c4 100644
--- a/libraries/kotlin.test/junit/src/main/kotlin/JUnitSupport.kt
+++ b/libraries/kotlin.test/junit/src/main/kotlin/JUnitSupport.kt
@@ -35,7 +35,9 @@ object JUnitAsserter : Asserter {
         Assert.assertNull(message ?: "actual value is not null", actual)
     }
 
-    override fun fail(message : String?) {
+    override fun fail(message : String?): Nothing {
         Assert.fail(message)
+        // should not get here
+        throw AssertionError(message)
     }
 }
diff --git a/libraries/kotlin.test/shared/src/main/kotlin.jvm/kotlin/test/TestAssertionsJVM.kt b/libraries/kotlin.test/shared/src/main/kotlin.jvm/kotlin/test/TestAssertionsJVM.kt
index df406968306..6502211ef28 100644
--- a/libraries/kotlin.test/shared/src/main/kotlin.jvm/kotlin/test/TestAssertionsJVM.kt
+++ b/libraries/kotlin.test/shared/src/main/kotlin.jvm/kotlin/test/TestAssertionsJVM.kt
@@ -22,11 +22,9 @@ fun <T : Throwable> assertFailsWith(exceptionClass: Class<T>, message: String?,
             return e as T
         }
         asserter.fail((message?.let { "$it. " } ?: "") + "Expected an exception of type $exceptionClass to be thrown, but was $e")
-        throw e
     }
     val msg = message?.let { "$it. " } ?: ""
     asserter.fail(msg + "Expected an exception of type $exceptionClass to be thrown, but was completed successfully.")
-    throw IllegalStateException(msg + "Should have failed.")
 }
 
 /** Asserts that a [block] fails with a specific exception of type [exceptionClass] being thrown. */
diff --git a/libraries/kotlin.test/shared/src/main/kotlin/kotlin/test/DefaultAsserter.kt b/libraries/kotlin.test/shared/src/main/kotlin/kotlin/test/DefaultAsserter.kt
index eed8581329a..b5cedf80a61 100644
--- a/libraries/kotlin.test/shared/src/main/kotlin/kotlin/test/DefaultAsserter.kt
+++ b/libraries/kotlin.test/shared/src/main/kotlin/kotlin/test/DefaultAsserter.kt
@@ -5,7 +5,7 @@ package kotlin.test
  */
 class DefaultAsserter() : Asserter {
 
-    override fun fail(message: String?) {
+    override fun fail(message: String?): Nothing {
         if (message == null)
             throw AssertionError()
         else
diff --git a/libraries/kotlin.test/shared/src/main/kotlin/kotlin/test/TestAssertions.kt b/libraries/kotlin.test/shared/src/main/kotlin/kotlin/test/TestAssertions.kt
index 635b3a4395f..4d7699b6727 100644
--- a/libraries/kotlin.test/shared/src/main/kotlin/kotlin/test/TestAssertions.kt
+++ b/libraries/kotlin.test/shared/src/main/kotlin/kotlin/test/TestAssertions.kt
@@ -63,7 +63,7 @@ fun assertNull(actual: Any?, message: String? = null) {
 }
 
 /** Marks a test as having failed if this point in the execution path is reached, with an optional [message]. */
-fun fail(message: String? = null) {
+fun fail(message: String? = null): Nothing {
     asserter.fail(message)
 }
 
@@ -81,16 +81,13 @@ fun <@OnlyInputTypes T> expect(expected: T, message: String?, block: () -> T) {
 fun fails(block: () -> Unit): Throwable? = assertFails(block)
 
 /** Asserts that given function [block] fails by throwing an exception. */
-fun assertFails(block: () -> Unit): Throwable? {
-    var thrown: Throwable? = null
+fun assertFails(block: () -> Unit): Throwable {
     try {
         block()
     } catch (e: Throwable) {
-        thrown = e
+        return e
     }
-    if (thrown == null)
-        asserter.fail("Expected an exception to be thrown")
-    return thrown
+    asserter.fail("Expected an exception to be thrown")
 }
 
 /**
@@ -103,7 +100,7 @@ interface Asserter {
      *
      * @param message the message to report.
      */
-    fun fail(message: String?): Unit
+    fun fail(message: String?): Nothing
 
     /**
      * Asserts that the specified value is `true`.