System.setProperty("abc.xyz", "789");

        value = "${abc.xyz}";
        assertEquals("789", ResourceUtil.resolve(value));

        value = "${abc}${abc.xyz}";
        assertEquals("123789", ResourceUtil.resolve(value));

        value = "xxx${abc.xyz}zzz";
        assertEquals("xxx789zzz", ResourceUtil.resolve(value));

        value = "${\\$}";
        assertEquals(value, ResourceUtil.resolve(value));

        assertEquals("abc 123 ", fessXpathTransformer.removeCommentTag("abc<!-- foo1 -->123<!-- foo2 -->"));
        assertEquals("abc 123 xyz", fessXpathTransformer.removeCommentTag("abc<!-- foo1 -->123<!-- foo2 -->xyz"));
        assertEquals("abc ", fessXpathTransformer.removeCommentTag("abc<!---->"));
        assertEquals("abc -->", fessXpathTransformer.removeCommentTag("abc<!-- foo-->-->"));