--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/test/jdk/java/net/httpclient/http2/java.net.http/jdk/internal/net/http/hpack/TestHelper.java	Wed Feb 07 21:45:37 2018 +0000
@@ -0,0 +1,164 @@
+/*
+ * Copyright (c) 2014, 2017, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+package jdk.internal.net.http.hpack;
+
+import org.testng.annotations.Test;
+
+import java.util.Objects;
+import java.util.Random;
+
+public final class TestHelper {
+
+    public static Random newRandom() {
+        long seed = Long.getLong("jdk.test.lib.random.seed", System.currentTimeMillis());
+        System.out.println("new java.util.Random(" + seed + ")");
+        return new Random(seed);
+    }
+
+    public static <T extends Throwable> T assertVoidThrows(Class<T> clazz, Block<?> code) {
+        return assertThrows(clazz, () -> {
+            code.run();
+            return null;
+        });
+    }
+
+    public static <T extends Throwable> T assertThrows(Class<T> clazz, ReturningBlock<?> code) {
+        Objects.requireNonNull(clazz, "clazz == null");
+        Objects.requireNonNull(code, "code == null");
+        try {
+            code.run();
+        } catch (Throwable t) {
+            if (clazz.isInstance(t)) {
+                return clazz.cast(t);
+            }
+            throw new AssertionError("Expected to catch exception of type "
+                    + clazz.getCanonicalName() + ", instead caught "
+                    + t.getClass().getCanonicalName(), t);
+
+        }
+        throw new AssertionError(
+                "Expected to catch exception of type " + clazz.getCanonicalName()
+                        + ", but caught nothing");
+    }
+
+    public static <T> T assertDoesNotThrow(ReturningBlock<T> code) {
+        Objects.requireNonNull(code, "code == null");
+        try {
+            return code.run();
+        } catch (Throwable t) {
+            throw new AssertionError(
+                    "Expected code block to exit normally, instead " +
+                            "caught " + t.getClass().getCanonicalName(), t);
+        }
+    }
+
+    public static void assertVoidDoesNotThrow(Block<?> code) {
+        Objects.requireNonNull(code, "code == null");
+        try {
+            code.run();
+        } catch (Throwable t) {
+            throw new AssertionError(
+                    "Expected code block to exit normally, instead " +
+                            "caught " + t.getClass().getCanonicalName(), t);
+        }
+    }
+
+
+    public static void assertExceptionMessageContains(Throwable t,
+                                                      CharSequence firstSubsequence,
+                                                      CharSequence... others) {
+        assertCharSequenceContains(t.getMessage(), firstSubsequence, others);
+    }
+
+    public static void assertCharSequenceContains(CharSequence s,
+                                                  CharSequence firstSubsequence,
+                                                  CharSequence... others) {
+        if (s == null) {
+            throw new NullPointerException("Exception message is null");
+        }
+        String str = s.toString();
+        String missing = null;
+        if (!str.contains(firstSubsequence.toString())) {
+            missing = firstSubsequence.toString();
+        } else {
+            for (CharSequence o : others) {
+                if (!str.contains(o.toString())) {
+                    missing = o.toString();
+                    break;
+                }
+            }
+        }
+        if (missing != null) {
+            throw new AssertionError("CharSequence '" + s + "'" + " does not "
+                    + "contain subsequence '" + missing + "'");
+        }
+    }
+
+    public interface ReturningBlock<T> {
+        T run() throws Throwable;
+    }
+
+    public interface Block<T> {
+        void run() throws Throwable;
+    }
+
+    // tests
+
+    @Test
+    public void assertThrows() {
+        assertThrows(NullPointerException.class, () -> ((Object) null).toString());
+    }
+
+    @Test
+    public void assertThrowsWrongType() {
+        try {
+            assertThrows(IllegalArgumentException.class, () -> ((Object) null).toString());
+        } catch (AssertionError e) {
+            Throwable cause = e.getCause();
+            String message = e.getMessage();
+            if (cause != null
+                    && cause instanceof NullPointerException
+                    && message != null
+                    && message.contains("instead caught")) {
+                return;
+            }
+        }
+        throw new AssertionError();
+    }
+
+    @Test
+    public void assertThrowsNoneCaught() {
+        try {
+            assertThrows(IllegalArgumentException.class, () -> null);
+        } catch (AssertionError e) {
+            Throwable cause = e.getCause();
+            String message = e.getMessage();
+            if (cause == null
+                    && message != null
+                    && message.contains("but caught nothing")) {
+                return;
+            }
+        }
+        throw new AssertionError();
+    }
+}