@Test
    void validYaml(JenkinsConfiguredWithCodeRule j) throws Exception {
        // Disable CSRF protection to simplify testing
        j.jenkins.setCrumbIssuer(null);

        WebResponse response = performYamlValidation(j, "jenkins:\n  systemMessage: \"Hello from test\"");

        assertThat(response.getStatusCode(), is(200));
        assertThat(response.getContentType(), is("application/json"));

        JSONArray jsonResponse = JSONArray.fromObject(response.getContentAsString());
        assertThat(jsonResponse.size(), is(0));
    }
Tests that valid YAML returns an empty array response.
test-harness/src/test/java/io/jenkins/plugins/casc/YamlValidationTest.java