Add some more fail tests

Author: patrickfav

src/main/java/at/favre/lib/bytes/Base64.java

@@ -74,7 +74,7 @@ public static byte[] decode(String in) {
             } else if (c == '\n' || c == '\r' || c == ' ' || c == '\t') {
                 continue;
             } else {
-                return null;
+                throw new IllegalArgumentException("invalid character to decode: " + c);
             }
 
             // Append this char's 6 bits to the word.

src/test/java/at/favre/lib/bytes/BytesParseAndEncodingTest.java

@@ -44,6 +44,11 @@ public void parseHex() throws Exception {
         assertArrayEquals(defaultArray, Bytes.parseHex(Bytes.parseHex("A0E1").encodeHex()).array());
     }
 
+    @Test(expected = IllegalArgumentException.class)
+    public void parseHexInvalid() throws Exception {
+        Bytes.parseHex("A0E");
+    }
+
     @Test
     public void encodeHex() throws Exception {
         byte[] defaultArray = new byte[]{(byte) 0xA0, (byte) 0xE1};
@@ -58,6 +63,11 @@ public void parseBase64() throws Exception {
         assertArrayEquals(encodingExample, Bytes.parseBase64("SpT9/x6v7Q==").array());
     }
 
+    @Test(expected = IllegalArgumentException.class)
+    public void parseBase64Invalid() throws Exception {
+        Bytes.parseBase64("☕");
+    }
+
     @Test
     public void encodeBase64() throws Exception {
         assertEquals("SpT9/x6v7Q==", Bytes.from(encodingExample).encodeBase64());