Add integration test for YAML validation error handling (#2628)

Author: AhmedFatthy1040

test-harness/src/test/java/io/jenkins/plugins/casc/YamlValidationTest.java

@@ -0,0 +1,125 @@
+package io.jenkins.plugins.casc;
+
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.hamcrest.Matchers.containsString;
+import static org.hamcrest.Matchers.equalTo;
+import static org.hamcrest.Matchers.is;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import io.jenkins.plugins.casc.misc.JenkinsConfiguredWithCodeRule;
+import io.jenkins.plugins.casc.misc.junit.jupiter.WithJenkinsConfiguredWithCode;
+import java.net.URL;
+import java.nio.charset.StandardCharsets;
+import java.text.MessageFormat;
+import net.sf.json.JSONArray;
+import org.htmlunit.HttpMethod;
+import org.htmlunit.WebClient;
+import org.htmlunit.WebRequest;
+import org.htmlunit.WebResponse;
+import org.junit.jupiter.api.Test;
+import org.jvnet.hudson.test.Issue;
+
+/**
+ * Tests for YAML validation in the Configuration-as-Code endpoint.
+ */
+@WithJenkinsConfiguredWithCode
+public class YamlValidationTest {
+
+    /**
+     * Tests that valid YAML returns an empty array response.
+     */
+    @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 YAML with incorrect indentation returns proper JSON response.
+     */
+    @Test
+    @Issue("2628")
+    void invalidIndentation(JenkinsConfiguredWithCodeRule j) throws Exception {
+        j.jenkins.setCrumbIssuer(null);
+        
+        WebResponse response = performYamlValidation(j, 
+                "jenkins:\nsystemMessage: \"Bad indentation\"");
+        
+        assertThat(response.getContentType(), is("application/json"));
+        
+        // Verify the response contains valid JSON regardless of status code
+        String responseString = response.getContentAsString();
+        JSONArray jsonResponse = JSONArray.fromObject(responseString);
+        
+        // The response should be a non-empty JSON array
+        assertThat("Should return error details", jsonResponse.size() > 0, is(true));
+    }
+    
+    /**
+     * Tests that YAML with invalid structure returns proper JSON response.
+     */
+    @Test
+    @Issue("2628")
+    void invalidStructure(JenkinsConfiguredWithCodeRule j) throws Exception {
+        j.jenkins.setCrumbIssuer(null);
+        
+        WebResponse response = performYamlValidation(j, 
+                "jenkins:\n  numExecutors: {");
+        
+        assertThat(response.getContentType(), is("application/json"));
+        
+        // Verify the response contains valid JSON regardless of status code
+        String responseString = response.getContentAsString();
+        JSONArray jsonResponse = JSONArray.fromObject(responseString);
+        
+        // The response should be a non-empty JSON array
+        assertThat("Should return error details", jsonResponse.size() > 0, is(true));
+    }
+    
+    /**
+     * Tests that YAML with unknown property returns proper JSON response.
+     */
+    @Test
+    @Issue("2628")
+    void unknownProperty(JenkinsConfiguredWithCodeRule j) throws Exception {
+        j.jenkins.setCrumbIssuer(null);
+        
+        WebResponse response = performYamlValidation(j, 
+                "jenkins:\n  nonExistentProperty: \"This property doesn't exist\"\n  systemMessage: \"Valid property\"");
+        
+        assertThat(response.getContentType(), is("application/json"));
+        
+        // Verify the response contains valid JSON regardless of status code
+        String responseString = response.getContentAsString();
+        JSONArray jsonResponse = JSONArray.fromObject(responseString);
+        
+        // The response should be a non-empty JSON array with details about the unknown property
+        assertThat("Should return error details", jsonResponse.size() > 0, is(true));
+        assertThat(responseString, containsString("nonExistentProperty"));
+    }
+
+    /**
+     * Helper method to perform YAML validation.
+     */
+    private WebResponse performYamlValidation(JenkinsConfiguredWithCodeRule j, String yamlContent) throws Exception {
+        URL apiURL = new URL(MessageFormat.format("{0}configuration-as-code/check", j.getURL().toString()));
+        WebRequest request = new WebRequest(apiURL, HttpMethod.POST);
+        request.setCharset(StandardCharsets.UTF_8);
+        request.setRequestBody(yamlContent);
+        
+        WebClient client = j.createWebClient();
+        // Don't throw exceptions for error status codes
+        client.getOptions().setThrowExceptionOnFailingStatusCode(false);
+        
+        return client.getPage(request).getWebResponse();
+    }
+}