Add a test for removing modes.

Change-Id: I4d069ddb004f7da58f847002d5cec54ad2836f73
Reviewed-on: http://gerrit.dmdirc.com/3965
Reviewed-by: Greg Holmes <greg@dmdirc.com>
Automatic-Compile: DMDirc Build Manager

test/com/dmdirc/parser/irc/PrefixModeManagerTest.java

                 manager.insertMode(manager.insertMode(manager.insertMode("", 'n'), 'm'), 'o'));
     }
 
+    @Test
+    public void testRemoveMode() {
+        manager.add('m', '/');
+        manager.add('n', '+');
+        manager.add('o', '@');
+
+        assertEquals("", manager.removeMode("", 'm'));
+        assertEquals("", manager.removeMode("m", 'm'));
+        assertEquals("no", manager.removeMode("no", 'm'));
+        assertEquals("no", manager.removeMode("mno", 'm'));
+        assertEquals("mo", manager.removeMode("mno", 'n'));
+    }
+
     @Test
     public void testCompareImportantModes() {
         // No modes, must be equal