diff --git a/org.eclipse.lemminx/src/test/java/org/eclipse/lemminx/services/extensions/XMLCompletionExtensionTest.java b/org.eclipse.lemminx/src/test/java/org/eclipse/lemminx/services/extensions/XMLCompletionExtensionTest.java
new file mode 100644
index 000000000..a7778ced1
--- /dev/null
+++ b/org.eclipse.lemminx/src/test/java/org/eclipse/lemminx/services/extensions/XMLCompletionExtensionTest.java
@@ -0,0 +1,93 @@
+/*******************************************************************************
+* Copyright (c) 2024 Christoph Läubrich and others.
+* All rights reserved. This program and the accompanying materials
+* which accompanies this distribution, and is available at
+* http://www.eclipse.org/legal/epl-v20.html
+*
+* SPDX-License-Identifier: EPL-2.0
+*
+* Contributors:
+*     Christoph Läubrich - initial API and implementation
+*******************************************************************************/
+package org.eclipse.lemminx.services.extensions;
+
+import org.eclipse.lemminx.AbstractCacheBasedTest;
+import org.eclipse.lemminx.XMLAssert;
+import org.eclipse.lemminx.commons.BadLocationException;
+import org.eclipse.lemminx.services.XMLLanguageService;
+import org.eclipse.lemminx.services.extensions.completion.ICompletionParticipant;
+import org.eclipse.lemminx.services.extensions.completion.ICompletionRequest;
+import org.eclipse.lemminx.services.extensions.completion.ICompletionResponse;
+import org.eclipse.lsp4j.CompletionItem;
+import org.eclipse.lsp4j.jsonrpc.CancelChecker;
+import org.junit.jupiter.api.Test;
+
+/**
+ * XML completion tests which uses the {@link ICompletionParticipant}
+ */
+public class XMLCompletionExtensionTest extends AbstractCacheBasedTest {
+
+	private static final CompletionItem HELLO_WORLD_ITEM = XMLAssert.c("World", "World");
+
+	private final class TestCompletionParticipant implements ICompletionParticipant {
+		@Override
+		public void onXMLContent(ICompletionRequest request, ICompletionResponse response, CancelChecker cancelChecker)
+				throws Exception {
+			System.out.println("onXMLContent: " + request.getCurrentTag());
+			if (request.getCurrentTag().equals("hello")) {
+				response.addCompletionAttribute(HELLO_WORLD_ITEM);
+			}
+		}
+
+		@Override
+		public void onTagOpen(ICompletionRequest completionRequest, ICompletionResponse completionResponse,
+				CancelChecker cancelChecker) throws Exception {
+		}
+
+		@Override
+		public void onDTDSystemId(String valuePrefix, ICompletionRequest request, ICompletionResponse response,
+				CancelChecker cancelChecker) throws Exception {
+		}
+
+		@Override
+		public void onAttributeValue(String valuePrefix, ICompletionRequest request, ICompletionResponse response,
+				CancelChecker cancelChecker) throws Exception {
+		}
+
+		@Override
+		public void onAttributeName(boolean generateValue, ICompletionRequest request, ICompletionResponse response,
+				CancelChecker cancelChecker) throws Exception {
+		}
+	}
+
+	/**
+	 * Test that
+	 * {@link ICompletionParticipant#onXMLContent(ICompletionRequest, ICompletionResponse, CancelChecker)}
+	 * is called for a simple content tag
+	 * 
+	 * @throws BadLocationException
+	 */
+	@Test
+	public void testSimpleCompletion() throws BadLocationException {
+		XMLLanguageService service = new XMLLanguageService();
+		service.registerCompletionParticipant(new TestCompletionParticipant());
+		XMLAssert.testCompletionFor(service, "<hello>|</hello>", (String) null, null, null, null, true,
+				HELLO_WORLD_ITEM);
+	}
+
+	/**
+	 * Test that
+	 * {@link ICompletionParticipant#onXMLContent(ICompletionRequest, ICompletionResponse, CancelChecker)}
+	 * is called for a CDATA content tag
+	 * 
+	 * @throws BadLocationException
+	 */
+	@Test
+	public void testCDATACompletion() throws BadLocationException {
+		XMLLanguageService service = new XMLLanguageService();
+		service.registerCompletionParticipant(new TestCompletionParticipant());
+		XMLAssert.testCompletionFor(service, "<hello><![CDATA[|]]></hello>", (String) null, null, null, null, true,
+				HELLO_WORLD_ITEM);
+	}
+
+}