diff --git a/org.eclipse.lemminx/src/main/java/org/eclipse/lemminx/services/XMLLanguageService.java b/org.eclipse.lemminx/src/main/java/org/eclipse/lemminx/services/XMLLanguageService.java
index 923b8d141..e1116ff56 100644
--- a/org.eclipse.lemminx/src/main/java/org/eclipse/lemminx/services/XMLLanguageService.java
+++ b/org.eclipse.lemminx/src/main/java/org/eclipse/lemminx/services/XMLLanguageService.java
@@ -12,7 +12,6 @@
  */
 package org.eclipse.lemminx.services;
 
-import java.nio.file.Path;
 import java.util.List;
 import java.util.Map;
 import java.util.concurrent.CompletableFuture;
@@ -190,7 +189,7 @@ public List<Diagnostic> doDiagnostics(DOMDocument xmlDocument, XMLValidationSett
 		return diagnostics.doDiagnostics(xmlDocument, validationSettings, validationArgs, cancelChecker);
 	}
 
-	public CompletableFuture<Path> publishDiagnostics(DOMDocument xmlDocument,
+	public CompletableFuture<Void> publishDiagnostics(DOMDocument xmlDocument,
 			Consumer<PublishDiagnosticsParams> publishDiagnostics, Consumer<TextDocument> triggerValidation,
 			XMLValidationRootSettings validationSettings, Map<String, Object> validationArgs,
 			CancelChecker cancelChecker) {
@@ -218,6 +217,7 @@ public CompletableFuture<Path> publishDiagnostics(DOMDocument xmlDocument,
 				triggerValidation.accept(document);
 				return null;
 			});
+			return allFutures;
 		}
 		return null;
 	}
diff --git a/org.eclipse.lemminx/src/test/java/org/eclipse/lemminx/MockXMLLanguageClient.java b/org.eclipse.lemminx/src/test/java/org/eclipse/lemminx/MockXMLLanguageClient.java
index 3fd647de8..02591e15f 100644
--- a/org.eclipse.lemminx/src/test/java/org/eclipse/lemminx/MockXMLLanguageClient.java
+++ b/org.eclipse.lemminx/src/test/java/org/eclipse/lemminx/MockXMLLanguageClient.java
@@ -14,6 +14,7 @@
 import java.util.ArrayList;
 import java.util.List;
 import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.TimeUnit;
 
 import org.eclipse.lemminx.customservice.ActionableNotification;
 import org.eclipse.lemminx.customservice.XMLLanguageClientAPI;
@@ -98,6 +99,25 @@ public List<PublishDiagnosticsParams> getPublishDiagnostics() {
 		return publishDiagnostics;
 	}
 
+	/**
+	 * Wait until the total number of published diagnostics reaches the expected
+	 * count, or the timeout expires.
+	 */
+	public void waitForDiagnosticCount(int expectedCount, long timeoutMs) {
+		long deadline = System.currentTimeMillis() + timeoutMs;
+		while (publishDiagnostics.size() < expectedCount) {
+			if (System.currentTimeMillis() >= deadline) {
+				break;
+			}
+			try {
+				Thread.sleep(20);
+			} catch (InterruptedException e) {
+				Thread.currentThread().interrupt();
+				break;
+			}
+		}
+	}
+
 	public List<MessageParams> getLogMessages() {
 		return logMessages;
 	}
diff --git a/org.eclipse.lemminx/src/test/java/org/eclipse/lemminx/MockXMLLanguageServer.java b/org.eclipse.lemminx/src/test/java/org/eclipse/lemminx/MockXMLLanguageServer.java
index 6ee753114..b0090200e 100644
--- a/org.eclipse.lemminx/src/test/java/org/eclipse/lemminx/MockXMLLanguageServer.java
+++ b/org.eclipse.lemminx/src/test/java/org/eclipse/lemminx/MockXMLLanguageServer.java
@@ -46,6 +46,10 @@ public List<PublishDiagnosticsParams> getPublishDiagnostics() {
 		return getLanguageClient().getPublishDiagnostics();
 	}
 
+	public void waitForDiagnosticCount(int expectedCount, long timeoutMs) {
+		getLanguageClient().waitForDiagnosticCount(expectedCount, timeoutMs);
+	}
+
 	@Override
 	public MockXMLLanguageClient getLanguageClient() {
 		return (MockXMLLanguageClient) super.getLanguageClient();
diff --git a/org.eclipse.lemminx/src/test/java/org/eclipse/lemminx/XMLAssert.java b/org.eclipse.lemminx/src/test/java/org/eclipse/lemminx/XMLAssert.java
index 4ee6e1930..abff9df5f 100644
--- a/org.eclipse.lemminx/src/test/java/org/eclipse/lemminx/XMLAssert.java
+++ b/org.eclipse.lemminx/src/test/java/org/eclipse/lemminx/XMLAssert.java
@@ -22,7 +22,6 @@
 import static org.junit.jupiter.api.Assertions.assertTrue;
 import static org.junit.jupiter.api.Assertions.fail;
 
-import java.nio.file.Path;
 import java.nio.file.Paths;
 import java.util.ArrayList;
 import java.util.Arrays;
@@ -912,21 +911,41 @@ public static void publishDiagnostics(DOMDocument xmlDocument, List<PublishDiagn
 
 	public static void publishDiagnostics(DOMDocument xmlDocument, XMLValidationRootSettings validationSettings,
 			List<PublishDiagnosticsParams> actual, XMLLanguageService languageService) {
-		CompletableFuture<Path> error = languageService.publishDiagnostics(xmlDocument, params -> {
+		languageService.publishDiagnostics(xmlDocument, params -> {
 			actual.add(params);
 		}, (doc) -> {
-			// Retrigger validation
-			publishDiagnostics(xmlDocument, actual, languageService);
 		}, validationSettings, Collections.emptyMap(), () -> {
 		});
+	}
+
+	/**
+	 * Await completion of any in-progress resource downloads (XSD, DTD) for the
+	 * given XML content. This replaces Thread.sleep() calls in tests that need to
+	 * wait for async downloads to complete before re-validating.
+	 */
+	public static void awaitDownloads(XMLLanguageService ls, String xml, String fileURI) {
+		awaitDownloads(ls, xml, fileURI, null);
+	}
 
-		if (error != null) {
+	/**
+	 * Await completion of any in-progress resource downloads (XSD, DTD) for the
+	 * given XML content. This replaces Thread.sleep() calls in tests that need to
+	 * wait for async downloads to complete before re-validating.
+	 */
+	public static void awaitDownloads(XMLLanguageService ls, String xml, String fileURI,
+			XMLValidationRootSettings validationSettings) {
+		DOMDocument xmlDocument = DOMParser.getInstance().parse(xml, fileURI, ls.getResolverExtensionManager());
+		ls.setDocumentProvider((uri) -> xmlDocument);
+		CompletableFuture<Void> downloadsFuture = ls.publishDiagnostics(xmlDocument,
+				params -> {
+				}, (doc) -> {
+				}, validationSettings, Collections.emptyMap(), () -> {
+				});
+		if (downloadsFuture != null) {
 			try {
-				error.join();
-				// Wait for 500 ms to collect the last params
-				Thread.sleep(200);
+				downloadsFuture.get(10, java.util.concurrent.TimeUnit.SECONDS);
 			} catch (Exception e) {
-				e.printStackTrace();
+				// Expected - downloads may fail
 			}
 		}
 	}
diff --git a/org.eclipse.lemminx/src/test/java/org/eclipse/lemminx/extensions/contentmodel/BaseFileTempTest.java b/org.eclipse.lemminx/src/test/java/org/eclipse/lemminx/extensions/contentmodel/BaseFileTempTest.java
index 9cfafb10b..b91838295 100644
--- a/org.eclipse.lemminx/src/test/java/org/eclipse/lemminx/extensions/contentmodel/BaseFileTempTest.java
+++ b/org.eclipse.lemminx/src/test/java/org/eclipse/lemminx/extensions/contentmodel/BaseFileTempTest.java
@@ -18,6 +18,8 @@
 import java.nio.file.Path;
 import java.nio.file.Paths;
 import java.nio.file.StandardOpenOption;
+import java.nio.file.attribute.FileTime;
+import java.time.Instant;
 
 import org.eclipse.lemminx.AbstractCacheBasedTest;
 
@@ -39,16 +41,12 @@ protected static void updateFile(String fileName, String contents) throws IOExce
 		updateFile(fileURI, contents);
 	}
 	protected static void updateFile(URI fileURI, String contents) throws IOException {
-		// For Mac OS, Linux OS, the call of Files.getLastModifiedTime is working for 1
-		// second.
-		// Here we wait for > 1s to be sure that call of Files.getLastModifiedTime will
-		// work.
-		try {
-			Thread.sleep(1050);
-		} catch (InterruptedException e) {
-			Thread.currentThread().interrupt();
-		}
 		createFile(fileURI, contents);
+		// Set the last modified time 2 seconds into the future to ensure
+		// Files.getLastModifiedTime detects the change (filesystem timestamp
+		// resolution on macOS/Linux is 1 second).
+		Path path = Paths.get(fileURI);
+		Files.setLastModifiedTime(path, FileTime.from(Instant.now().plusSeconds(2)));
 	}
 
 	protected Path getTempDirPath() {
diff --git a/org.eclipse.lemminx/src/test/java/org/eclipse/lemminx/extensions/contentmodel/XMLExternalTest.java b/org.eclipse.lemminx/src/test/java/org/eclipse/lemminx/extensions/contentmodel/XMLExternalTest.java
index 97aa8d53e..598243d6c 100644
--- a/org.eclipse.lemminx/src/test/java/org/eclipse/lemminx/extensions/contentmodel/XMLExternalTest.java
+++ b/org.eclipse.lemminx/src/test/java/org/eclipse/lemminx/extensions/contentmodel/XMLExternalTest.java
@@ -41,7 +41,6 @@
  */
 public class XMLExternalTest extends BaseFileTempTest {
 
-	private int threadSleepMs = 600;
 	private MockXMLLanguageServer languageServer;
 
 	@BeforeEach
@@ -79,7 +78,7 @@ public void externalDTDTest() throws InterruptedException, IOException {
 
 		clientOpenFile(languageServer, xmlTextDocument);
 
-		Thread.sleep(threadSleepMs);
+		languageServer.waitForDiagnosticCount(1, 5000);
 
 		List<PublishDiagnosticsParams> actualDiagnostics = languageServer.getPublishDiagnostics();
 		assertEquals(1, actualDiagnostics.size());
@@ -88,7 +87,7 @@ public void externalDTDTest() throws InterruptedException, IOException {
 		editFile(testDtd, 2, "");
 		didChangedWatchedFiles(languageServer, testDtd);
 
-		Thread.sleep(threadSleepMs);
+		languageServer.waitForDiagnosticCount(2, 5000);
 
 		assertEquals(2, actualDiagnostics.size());
 		assertFalse(actualDiagnostics.get(1).getDiagnostics().isEmpty());
@@ -134,7 +133,7 @@ public void externalXSDTest() throws InterruptedException, IOException {
 
 		clientOpenFile(languageServer, xmlTextDocument);
 
-		Thread.sleep(threadSleepMs);
+		languageServer.waitForDiagnosticCount(1, 5000);
 
 		List<PublishDiagnosticsParams> actualDiagnostics = languageServer.getPublishDiagnostics();
 		assertEquals(1, actualDiagnostics.size());
@@ -143,7 +142,7 @@ public void externalXSDTest() throws InterruptedException, IOException {
 		editFile(testXsd, 12, "            maxOccurs=\"2\"/>");
 		didChangedWatchedFiles(languageServer, testXsd);
 
-		Thread.sleep(threadSleepMs);
+		languageServer.waitForDiagnosticCount(2, 5000);
 
 		assertEquals(2, actualDiagnostics.size());
 		assertEquals("cvc-complex-type.2.4.f", actualDiagnostics.get(1).getDiagnostics().get(0).getCode().getLeft());
diff --git a/org.eclipse.lemminx/src/test/java/org/eclipse/lemminx/extensions/contentmodel/XMLSchemaPublishDiagnosticsTest.java b/org.eclipse.lemminx/src/test/java/org/eclipse/lemminx/extensions/contentmodel/XMLSchemaPublishDiagnosticsTest.java
index 1e3d79b4f..a2ceb3825 100644
--- a/org.eclipse.lemminx/src/test/java/org/eclipse/lemminx/extensions/contentmodel/XMLSchemaPublishDiagnosticsTest.java
+++ b/org.eclipse.lemminx/src/test/java/org/eclipse/lemminx/extensions/contentmodel/XMLSchemaPublishDiagnosticsTest.java
@@ -16,7 +16,6 @@
 import static org.eclipse.lemminx.XMLAssert.r;
 import static org.eclipse.lemminx.XMLAssert.d;
 
-import java.util.concurrent.TimeUnit;
 import java.util.function.Consumer;
 
 import org.eclipse.lemminx.AbstractCacheBasedTest;
@@ -146,8 +145,6 @@ public void schemaWithUrlWithCache() throws Exception {
 				"</invoice> \r\n" + //
 				"";
 
-		TimeUnit.SECONDS.sleep(2); // HACK: to make the timing work on slow machines
-
 		// Downloading...
 		XMLAssert.testPublishDiagnosticsFor(xml, fileURI, ls, pd(fileURI,
 				new Diagnostic(r(2, 32, 2, 50),
@@ -156,7 +153,7 @@ public void schemaWithUrlWithCache() throws Exception {
 				new Diagnostic(r(1, 1, 1, 8), "cvc-elt.1.a: Cannot find the declaration of element 'invoice'.",
 						DiagnosticSeverity.Error, "xml", XMLSchemaErrorCode.cvc_elt_1_a.getCode())));
 
-		TimeUnit.SECONDS.sleep(5); // HACK: to make the timing work on slow machines
+		XMLAssert.awaitDownloads(ls, xml, fileURI);
 
 		// Downloaded error
 		XMLAssert.testPublishDiagnosticsFor(xml, fileURI, ls, pd(fileURI,
diff --git a/org.eclipse.lemminx/src/test/java/org/eclipse/lemminx/extensions/contentmodel/XMLValidationExternalResourcesBasedOnDTDTest.java b/org.eclipse.lemminx/src/test/java/org/eclipse/lemminx/extensions/contentmodel/XMLValidationExternalResourcesBasedOnDTDTest.java
index 16a67032c..1d9101639 100644
--- a/org.eclipse.lemminx/src/test/java/org/eclipse/lemminx/extensions/contentmodel/XMLValidationExternalResourcesBasedOnDTDTest.java
+++ b/org.eclipse.lemminx/src/test/java/org/eclipse/lemminx/extensions/contentmodel/XMLValidationExternalResourcesBasedOnDTDTest.java
@@ -17,8 +17,6 @@
 import static org.eclipse.lemminx.XMLAssert.r;
 import static org.eclipse.lemminx.XMLAssert.testCodeActionsFor;
 
-import java.util.concurrent.TimeUnit;
-
 import org.eclipse.lemminx.AbstractCacheBasedTest;
 import org.eclipse.lemminx.XMLAssert;
 import org.eclipse.lemminx.extensions.contentmodel.model.ContentModelManager;
@@ -96,7 +94,7 @@ public void docTypeDownloadProblem() throws Exception {
 						new Diagnostic(r(1, 1, 1, 13), "Element type \"root-element\" must be declared.",
 								DiagnosticSeverity.Error, "xml", DTDErrorCode.MSG_ELEMENT_NOT_DECLARED.getCode())));
 
-		TimeUnit.SECONDS.sleep(5); // HACK: to make the timing work on slow machines
+		XMLAssert.awaitDownloads(ls, xml, fileURI, validation);
 
 		// Downloaded error
 		XMLAssert.testPublishDiagnosticsFor(xml, fileURI, validation, ls,
@@ -177,7 +175,7 @@ public void entityRefDownloadProblem() throws Exception {
 						new Diagnostic(r(6, 1, 6, 7), "The entity \"abcd\" was referenced, but not declared.",
 								DiagnosticSeverity.Error, "xml", DTDErrorCode.EntityNotDeclared.getCode())));
 
-		TimeUnit.SECONDS.sleep(5); // HACK: to make the timing work on slow machines
+		XMLAssert.awaitDownloads(ls, xml, fileURI, validation);
 
 		// Downloaded error
 		XMLAssert.testPublishDiagnosticsFor(xml, fileURI, validation, ls,
diff --git a/org.eclipse.lemminx/src/test/java/org/eclipse/lemminx/extensions/contentmodel/XMLValidationExternalResourcesBasedOnXSDTest.java b/org.eclipse.lemminx/src/test/java/org/eclipse/lemminx/extensions/contentmodel/XMLValidationExternalResourcesBasedOnXSDTest.java
index fd3a59d55..119e1045a 100644
--- a/org.eclipse.lemminx/src/test/java/org/eclipse/lemminx/extensions/contentmodel/XMLValidationExternalResourcesBasedOnXSDTest.java
+++ b/org.eclipse.lemminx/src/test/java/org/eclipse/lemminx/extensions/contentmodel/XMLValidationExternalResourcesBasedOnXSDTest.java
@@ -17,8 +17,6 @@
 import static org.eclipse.lemminx.XMLAssert.r;
 import static org.eclipse.lemminx.XMLAssert.testCodeActionsFor;
 
-import java.util.concurrent.TimeUnit;
-
 import org.eclipse.lemminx.AbstractCacheBasedTest;
 import org.eclipse.lemminx.XMLAssert;
 import org.eclipse.lemminx.extensions.contentmodel.model.ContentModelManager;
@@ -99,7 +97,7 @@ public void noNamespaceSchemaLocationDownloadProblem() throws Exception {
 				new Diagnostic(r(0, 1, 0, 13), "cvc-elt.1.a: Cannot find the declaration of element 'root-element'.",
 						DiagnosticSeverity.Error, "xml", XMLSchemaErrorCode.cvc_elt_1_a.getCode())));
 
-		TimeUnit.SECONDS.sleep(5); // HACK: to make the timing work on slow machines
+		XMLAssert.awaitDownloads(ls, xml, fileURI, validation);
 
 		// Downloaded error
 		XMLAssert.testPublishDiagnosticsFor(xml, fileURI, validation, ls, pd(fileURI,
@@ -173,7 +171,7 @@ public void schemaLocationDownloadProblem() throws Exception {
 				new Diagnostic(r(0, 1, 0, 13), "cvc-elt.1.a: Cannot find the declaration of element 'root-element'.",
 						DiagnosticSeverity.Error, "xml", XMLSchemaErrorCode.cvc_elt_1_a.getCode())));
 
-		TimeUnit.SECONDS.sleep(5); // HACK: to make the timing work on slow machines
+		XMLAssert.awaitDownloads(ls, xml, fileURI, validation);
 
 		// Downloaded error
 		XMLAssert.testPublishDiagnosticsFor(xml, fileURI, validation, ls, pd(fileURI,
diff --git a/org.eclipse.lemminx/src/test/java/org/eclipse/lemminx/extensions/contentmodel/commands/XMLValidationCommandTest.java b/org.eclipse.lemminx/src/test/java/org/eclipse/lemminx/extensions/contentmodel/commands/XMLValidationCommandTest.java
index 44b070f5d..ec3076b9c 100644
--- a/org.eclipse.lemminx/src/test/java/org/eclipse/lemminx/extensions/contentmodel/commands/XMLValidationCommandTest.java
+++ b/org.eclipse.lemminx/src/test/java/org/eclipse/lemminx/extensions/contentmodel/commands/XMLValidationCommandTest.java
@@ -86,10 +86,8 @@ public void validationFileCommand() throws Exception {
 			// Open the XML document, the validation is triggered asynchronously
 			TextDocumentIdentifier xmlIdentifier = languageServer.didOpen("test.xml", xml);
 
-			// Wait for:
-			// - downloading of XSD from the HTTP server to lemminx cache
-			// - validation triggers
-			Thread.sleep(1000);
+			// Wait for downloading of XSD and validation to trigger
+			languageServer.waitForDiagnosticCount(2, 5000);
 
 			// 1.1 Validation test
 
@@ -141,10 +139,8 @@ public void validationFileCommand() throws Exception {
 			// Execute command cache
 			languageServer.executeCommand(XMLValidationFileCommand.COMMAND_ID, xmlIdentifier).get();
 
-			// Wait for:
-			// - downloading of XSD from the HTTP server to lemminx cache
-			// - validation triggers
-			Thread.sleep(1000);
+			// Wait for downloading and validation to trigger
+			languageServer.waitForDiagnosticCount(2, 5000);
 
 			// 3.1 Validation test
 
@@ -224,9 +220,8 @@ public void validationAllFilesCommand() throws Exception {
 			// Open the XML document, the validation is triggered asynchronously
 			TextDocumentIdentifier xml1Identifier = languageServer.didOpen("test1.xml", xml1);
 
-			// Wait for to collect diagnostics in the proper order (XSD diagnostics followed
-			// by DTD diagnostics)
-			Thread.sleep(2000);
+			// Wait for XSD diagnostics before opening second file
+			languageServer.waitForDiagnosticCount(2, 5000);
 
 			// Open the second XML file bound to the DTD
 			String xml2 = "<?xml version=\"1.0\" encoding=\"UTF-8\" ?>\r\n" + //
@@ -238,10 +233,8 @@ public void validationAllFilesCommand() throws Exception {
 			// Open the XML document, the validation is triggered asynchronously
 			TextDocumentIdentifier xml2Identifier = languageServer.didOpen("test2.xml", xml2);
 
-			// Wait for:
-			// - downloading of XSD from the HTTP server to lemminx cache
-			// - validation triggers
-			Thread.sleep(1000);
+			// Wait for all 4 diagnostics (2 for each XML file)
+			languageServer.waitForDiagnosticCount(4, 5000);
 
 			// 1.1 Validation test
 
@@ -316,13 +309,10 @@ public void validationAllFilesCommand() throws Exception {
 			XMLAssert.assertCompletion(list2, c("tag", "<tag />"), 5 /* region, endregion, cdata, comment, tag */);
 
 			// Execute command cache
-			Thread.sleep(1000);
 			languageServer.executeCommand(XMLValidationAllFilesCommand.COMMAND_ID).get();
 
-			// Wait for:
-			// - downloading of XSD from the HTTP server to lemminx cache
-			// - validation triggers
-			Thread.sleep(1000);
+			// Wait for downloading and validation to trigger (4 diagnostics: 2 per file)
+			languageServer.waitForDiagnosticCount(4, 5000);
 
 			// 3.1 Validation test
 
diff --git a/org.eclipse.lemminx/src/test/java/org/eclipse/lemminx/extensions/dtd/DTDValidationExternalResourcesTest.java b/org.eclipse.lemminx/src/test/java/org/eclipse/lemminx/extensions/dtd/DTDValidationExternalResourcesTest.java
index 4a867a602..f421073c3 100644
--- a/org.eclipse.lemminx/src/test/java/org/eclipse/lemminx/extensions/dtd/DTDValidationExternalResourcesTest.java
+++ b/org.eclipse.lemminx/src/test/java/org/eclipse/lemminx/extensions/dtd/DTDValidationExternalResourcesTest.java
@@ -17,8 +17,6 @@
 import static org.eclipse.lemminx.XMLAssert.r;
 import static org.eclipse.lemminx.XMLAssert.testCodeActionsFor;
 
-import java.util.concurrent.TimeUnit;
-
 import org.eclipse.lemminx.AbstractCacheBasedTest;
 import org.eclipse.lemminx.XMLAssert;
 import org.eclipse.lemminx.extensions.contentmodel.model.ContentModelManager;
@@ -121,7 +119,7 @@ public void entityRefDownloadProblem() throws Exception {
 								DiagnosticSeverity.Information, "xml",
 								ExternalResourceErrorCode.DownloadingResource.getCode())));
 
-		TimeUnit.SECONDS.sleep(5); // HACK: to make the timing work on slow machines
+		XMLAssert.awaitDownloads(ls, dtd, fileURI, validation);
 
 		// Downloaded error
 		XMLAssert.testPublishDiagnosticsFor(dtd, fileURI, validation, ls,
diff --git a/org.eclipse.lemminx/src/test/java/org/eclipse/lemminx/extensions/xsd/XSDValidationExternalResourcesTest.java b/org.eclipse.lemminx/src/test/java/org/eclipse/lemminx/extensions/xsd/XSDValidationExternalResourcesTest.java
index 2b3976e78..9b27f7741 100644
--- a/org.eclipse.lemminx/src/test/java/org/eclipse/lemminx/extensions/xsd/XSDValidationExternalResourcesTest.java
+++ b/org.eclipse.lemminx/src/test/java/org/eclipse/lemminx/extensions/xsd/XSDValidationExternalResourcesTest.java
@@ -17,8 +17,6 @@
 import static org.eclipse.lemminx.XMLAssert.r;
 import static org.eclipse.lemminx.XMLAssert.testCodeActionsFor;
 
-import java.util.concurrent.TimeUnit;
-
 import org.eclipse.lemminx.AbstractCacheBasedTest;
 import org.eclipse.lemminx.XMLAssert;
 import org.eclipse.lemminx.extensions.contentmodel.model.ContentModelManager;
@@ -96,7 +94,7 @@ public void includeSchemaLocationDownloadProblem() throws Exception {
 								DiagnosticSeverity.Information, "xsd",
 								ExternalResourceErrorCode.DownloadingResource.getCode())));
 
-		TimeUnit.SECONDS.sleep(5); // HACK: to make the timing work on slow machines
+		XMLAssert.awaitDownloads(ls, xsd, fileURI, validation);
 
 		// Downloaded error
 		XMLAssert.testPublishDiagnosticsFor(xsd, fileURI, validation, ls,
diff --git a/org.eclipse.lemminx/src/test/java/org/eclipse/lemminx/services/extensions/DocumentLifecycleParticipantTest.java b/org.eclipse.lemminx/src/test/java/org/eclipse/lemminx/services/extensions/DocumentLifecycleParticipantTest.java
index e8002611b..ea056d6e3 100644
--- a/org.eclipse.lemminx/src/test/java/org/eclipse/lemminx/services/extensions/DocumentLifecycleParticipantTest.java
+++ b/org.eclipse.lemminx/src/test/java/org/eclipse/lemminx/services/extensions/DocumentLifecycleParticipantTest.java
@@ -93,7 +93,7 @@ public void initializeLanguageService() {
 	public void didOpen() {
 		assertEquals(0, documentLifecycleParticipant.getDidOpen());
 		server.didOpen("test.xml", "<foo ");
-		waitFor();
+		waitUntil(() -> documentLifecycleParticipant.getDidOpen() >= 1);
 		assertEquals(1, documentLifecycleParticipant.getDidOpen());
 	}
 
@@ -102,7 +102,7 @@ public void didChange() {
 		assertEquals(0, documentLifecycleParticipant.getDidChange());
 		server.didOpen("test.xml", "<foo ");
 		server.didChange("test.xml", Collections.emptyList());
-		waitFor();
+		waitUntil(() -> documentLifecycleParticipant.getDidChange() >= 1);
 		assertEquals(1, documentLifecycleParticipant.getDidChange());
 	}
 
@@ -111,7 +111,7 @@ public void didSave() {
 		assertEquals(0, documentLifecycleParticipant.getDidSave());
 		server.didOpen("test.xml", "<foo ");
 		server.didSave("test.xml");
-		waitFor();
+		waitUntil(() -> documentLifecycleParticipant.getDidSave() >= 1);
 		assertEquals(1, documentLifecycleParticipant.getDidSave());
 	}
 
@@ -123,10 +123,18 @@ public void didClose() {
 		assertEquals(1, documentLifecycleParticipant.getDidClose());
 	}
 
-	private static void waitFor() {
-		try {
-			Thread.sleep(600);
-		} catch (Exception e) {
+	private static void waitUntil(java.util.function.BooleanSupplier condition) {
+		long deadline = System.currentTimeMillis() + 5000;
+		while (!condition.getAsBoolean()) {
+			if (System.currentTimeMillis() >= deadline) {
+				break;
+			}
+			try {
+				Thread.sleep(20);
+			} catch (InterruptedException e) {
+				Thread.currentThread().interrupt();
+				break;
+			}
 		}
 	}
 }
diff --git a/org.eclipse.lemminx/src/test/java/org/eclipse/lemminx/uriresolver/CacheResourcesManagerTest.java b/org.eclipse.lemminx/src/test/java/org/eclipse/lemminx/uriresolver/CacheResourcesManagerTest.java
index 45a790abb..8e9dbdf82 100644
--- a/org.eclipse.lemminx/src/test/java/org/eclipse/lemminx/uriresolver/CacheResourcesManagerTest.java
+++ b/org.eclipse.lemminx/src/test/java/org/eclipse/lemminx/uriresolver/CacheResourcesManagerTest.java
@@ -96,7 +96,7 @@ public void testUnavailableCache() throws Exception {
 			} catch (CacheResourceDownloadedException e) {
 			}
 		}
-		TimeUnit.SECONDS.sleep(2); // wait past the cache expiration date
+		TimeUnit.MILLISECONDS.sleep(200); // wait past the cache expiration date
 		try {
 			cacheResourcesManager.getResource(uri);
 			fail("cacheResourcesManager should be busy re-downloading the url");
@@ -119,7 +119,7 @@ public void testAvailableCache() throws Exception {
 		assertNotNull(path);
 		assertNotNull(cacheResourcesManager.getResource(uri));
 		server.stop();
-		TimeUnit.SECONDS.sleep(2); // wait past the cache expiration date
+		TimeUnit.MILLISECONDS.sleep(200); // wait past the cache expiration date
 		cacheResourcesManager.getResource(uri);
 		// Manager should return cached content, even if server is offline
 		assertNotNull(cacheResourcesManager.getResource(uri));
@@ -194,7 +194,7 @@ public void handle(String target, Request baseRequest, HttpServletRequest reques
 	}
 
 	private Cache<String, CacheResourceDownloadedException> testingCache() {
-		return CacheBuilder.newBuilder().expireAfterWrite(1, TimeUnit.SECONDS).maximumSize(1).build();
+		return CacheBuilder.newBuilder().expireAfterWrite(100, TimeUnit.MILLISECONDS).maximumSize(1).build();
 	}
 
 }
\ No newline at end of file