Move TestRng to our JUnit helper package

Other test suites may find this useful, especially when trying
to defeat the pack file compression with random data files.

Change-Id: Ic00a4ac626af7a1c94d18ee99305e295b267b1a3
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>

org.eclipse.jgit.test/tst/org/eclipse/jgit/util/TestRng.java → org.eclipse.jgit.junit/src/org/eclipse/jgit/junit/TestRng.java

 /*
- * Copyright (C) 2008, Google Inc.
+ * Copyright (C) 2008-2010, Google Inc.
  * and other copyright owners as documented in the project's IP log.
  *
  * This program and the accompanying materials are made available
@@ -41,18 +41,31 @@
  * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
-package org.eclipse.jgit.util;
+package org.eclipse.jgit.junit;
 
 /** Toy RNG to ensure we get predictable numbers during unit tests. */
 public class TestRng {
 	private int next;
 
+	/**
+	 * Create a new random number generator, seeded by a string.
+	 *
+	 * @param seed
+	 *            seed to bootstrap, usually this is the test method name.
+	 */
 	public TestRng(final String seed) {
 		next = 0;
 		for (int i = 0; i < seed.length(); i++)
 			next = next * 11 + seed.charAt(i);
 	}
 
+	/**
+	 * Get the next {@code cnt} bytes of random data.
+	 *
+	 * @param cnt
+	 *            number of random bytes to produce.
+	 * @return array of {@code cnt} randomly generated bytes.
+	 */
 	public byte[] nextBytes(final int cnt) {
 		final byte[] r = new byte[cnt];
 		for (int i = 0; i < cnt; i++)
@@ -60,6 +73,9 @@ public byte[] nextBytes(final int cnt) {
 		return r;
 	}
 
+	/**
+	 * @return the next random integer.
+	 */
 	public int nextInt() {
 		next = next * 1103515245 + 12345;
 		return next;

org.eclipse.jgit.test/tst/org/eclipse/jgit/util/TemporaryBufferTest.java

@@ -48,6 +48,8 @@
 import java.io.IOException;
 import java.util.Arrays;
 
+import org.eclipse.jgit.junit.TestRng;
+
 import junit.framework.TestCase;
 
 public class TemporaryBufferTest extends TestCase {