Added a test for hex conversions in CPColor

Tests/AppKit/CPColorTest.j

@@ -0,0 +1,14 @@
+@import <AppKit/AppKit.j>
+
+@implementation CPColorTest : OJTestCase
+{
+}
+
+- (void)testHexStringConversion
+{
+    var colors = ['000000', '7E8EAB', 'FFFFFF'];
+    for (var i = 0; i < colors.length; ++i)
+        [self assert: colors[i] equals: [[CPColor colorWithHexString: colors[i]] hexString]];
+}
+
+@end