@Test
    void verifyOperation() {
        val resolver = SpringExpressionLanguageValueResolver.getInstance();

        assertNotNull(resolver.apply("HelloWorld"));

        assertEquals("Hello World", resolver.resolve("${'Hello World'}"));
        assertEquals("Literal Value", resolver.resolve("Literal Value"));
        assertEquals("Hello World!", resolver.resolve("${'Hello World'.concat('!')}"));

        System.setProperty("cas.user", "Apereo CAS");
        assertEquals("Apereo CAS", resolver.resolve("${#systemProperties['cas.user']}"));
        assertNotNull(resolver.resolve("${#environmentVars['HOME']}"));
        assertNotNull(resolver.resolve("${#uuid}"));
        assertNotNull(resolver.resolve("${#randomNumber2}"));
        assertNotNull(resolver.resolve("${#randomNumber4}"));
        assertNotNull(resolver.resolve("${#randomNumber6}"));
        assertNotNull(resolver.resolve("${#randomNumber8}"));

        assertNotNull(resolver.resolve("${#randomString4}"));
        assertNotNull(resolver.resolve("${#randomString6}"));
        assertNotNull(resolver.resolve("${#randomString8}"));

        System.setProperty("cas.dir", "etc/cas/config");
        assertEquals("file://etc/cas/config/file.json",
            resolver.resolve("file://${#systemProperties['cas.dir']}/file.json"));

        assertNotNull(resolver.resolve("${#localDateTime}"));
        assertNotNull(resolver.resolve("${#localDateTimeUtc}"));
        assertNotNull(resolver.resolve("${#localDate}"));
        assertNotNull(resolver.resolve("${#localDateUtc}"));
        assertNotNull(resolver.resolve("${#zonedDateTime}"));
        assertNotNull(resolver.resolve("${#zonedDateTimeUtc}"));
        
        assertNotNull(resolver.resolve("${#applicationContext.get().id}"));
    }
This is {@link SpringExpressionLanguageValueResolverTests}.

@author Misagh Moayyed
@since 6.2.0
core/cas-server-core-util/src/test/java/org/apereo/cas/util/spring/SpringExpressionLanguageValueResolverTests.java