Add unit tests for hudson.cli.HexDump (#4058)

* Add unit tests for hudson.cli.HexDump

These tests were written using Diffblue Cover.

* Changed byte arrays to work for windows

cli/src/test/java/hudson/cli/HexDumpTest.java

+package hudson.cli;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+public class HexDumpTest {
+
+  @Test
+  public void testToHex1() {
+    Assert.assertEquals("'fooBar'",
+            HexDump.toHex(new byte[] {'f', 'o', 'o', 'B', 'a', 'r'}));
+    Assert.assertEquals("0xc3",
+            HexDump.toHex(new byte[] {(byte)'Ã'}));
+    Assert.assertEquals("0xac '100'",
+            HexDump.toHex(new byte[] {(byte)'€', '1', '0', '0'}));
+    Assert.assertEquals("'1' 0xf7 '2'",
+            HexDump.toHex(new byte[] {'1', (byte)'÷', '2'}));
+    Assert.assertEquals("'foo' 0x0a\n'Bar'",
+            HexDump.toHex(new byte[] {'f', 'o', 'o', '\n', 'B', 'a', 'r'}));
+  }
+
+  @Test
+  public void testToHex2() {
+    Assert.assertEquals("'ooBa'",
+            HexDump.toHex(new byte[] {'f', 'o', 'o', 'B', 'a', 'r'}, 1, 4));
+    Assert.assertEquals("0xc3",
+            HexDump.toHex(new byte[] {(byte)'Ã'}, 0, 1));
+    Assert.assertEquals("0xac '10'",
+            HexDump.toHex(new byte[] {(byte)'€', '1', '0', '0'}, 0, 3));
+    Assert.assertEquals("0xf7 '2'",
+            HexDump.toHex(new byte[] {'1', (byte)'÷', '2'}, 1, 2));
+    Assert.assertEquals("'Bar'",
+            HexDump.toHex(new byte[] {'f', 'o', 'o', '\n', 'B', 'a', 'r'}, 4, 3));
+    Assert.assertEquals("",
+            HexDump.toHex(new byte[] {'f', 'o', 'o', 'B', 'a', 'r'}, 0, 0));
+  }
+}