Retain original TestEngine order after pruning

documentation/src/docs/asciidoc/release-notes/release-notes-6.0.0-RC2.adoc

@@ -24,7 +24,9 @@ guidance on upgrading from JUnit 5.x.y to 6.0.0.
 [[release-notes-6.0.0-RC2-junit-platform-bug-fixes]]
 ==== Bug Fixes
 
-* ❓
+* The `Launcher` (specifically `LauncherDiscoveryResult`) now retains the original
+  `TestEngine` registration order after pruning test engines without tests, thereby
+  ensuring reliable test execution order of multiple test engines.
 
 [[release-notes-6.0.0-RC2-junit-platform-deprecations-and-breaking-changes]]
 ==== Deprecations and Breaking Changes

junit-platform-launcher/src/main/java/org/junit/platform/launcher/core/LauncherDiscoveryResult.java

@@ -12,7 +12,6 @@
 
 import static java.util.Collections.unmodifiableMap;
 import static java.util.Objects.requireNonNull;
-import static java.util.stream.Collectors.toMap;
 import static org.apiguardian.api.API.Status.INTERNAL;
 
 import java.util.Collection;
@@ -96,12 +95,9 @@ public LauncherDiscoveryResult withRetainedEngines(Predicate<? super TestDescrip
 	}
 
 	private Map<TestEngine, EngineResultInfo> retainEngines(Predicate<? super TestDescriptor> predicate) {
-		// @formatter:off
-		return this.testEngineResults.entrySet()
-				.stream()
-				.filter(entry -> predicate.test(entry.getValue().getRootDescriptor()))
-				.collect(toMap(Map.Entry::getKey, Map.Entry::getValue));
-		// @formatter:on
+		var retainedEngines = new LinkedHashMap<>(this.testEngineResults);
+		retainedEngines.entrySet().removeIf(entry -> !predicate.test(entry.getValue().getRootDescriptor()));
+		return retainedEngines;
 	}
 
 	static class EngineResultInfo {

platform-tests/src/test/java/org/junit/platform/launcher/core/LauncherDiscoveryResultTests.java

@@ -0,0 +1,111 @@
+/*
+ * Copyright 2015-2025 the original author or authors.
+ *
+ * All rights reserved. This program and the accompanying materials are
+ * made available under the terms of the Eclipse Public License v2.0 which
+ * accompanies this distribution and is available at
+ *
+ * https://www.eclipse.org/legal/epl-v20.html
+ */
+
+package org.junit.platform.launcher.core;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
+
+import java.util.LinkedHashMap;
+import java.util.Map;
+
+import org.junit.jupiter.api.Test;
+import org.junit.platform.engine.EngineDiscoveryRequest;
+import org.junit.platform.engine.ExecutionRequest;
+import org.junit.platform.engine.TestDescriptor;
+import org.junit.platform.engine.TestEngine;
+import org.junit.platform.engine.UniqueId;
+import org.junit.platform.launcher.core.LauncherDiscoveryResult.EngineResultInfo;
+
+/**
+ * Unit tests for {@link LauncherDiscoveryResult}.
+ */
+class LauncherDiscoveryResultTests {
+
+	/**
+	 * @see <a href="https://github.com/junit-team/junit-framework/issues/4862">GitHub issue #4862</>
+	 */
+	@Test
+	void withRetainedEnginesRetainsLinkedHashMapSemantics() {
+		TestEngine engine1 = new DummyEngine1();
+		TestEngine engine2 = new DummyEngine2();
+		TestEngine engine3 = new DummyEngine3();
+		TestEngine engine4 = new DummyEngine4();
+
+		TestDescriptor rootDescriptor1 = mock();
+		TestDescriptor rootDescriptor2 = mock();
+		TestDescriptor rootDescriptor3 = mock();
+		TestDescriptor rootDescriptor4 = mock();
+		when(rootDescriptor1.isTest()).thenReturn(true);
+		when(rootDescriptor2.isTest()).thenReturn(false);
+		when(rootDescriptor3.isTest()).thenReturn(false);
+		when(rootDescriptor4.isTest()).thenReturn(true);
+
+		EngineResultInfo engineResultInfo1 = mock();
+		EngineResultInfo engineResultInfo2 = mock();
+		EngineResultInfo engineResultInfo3 = mock();
+		EngineResultInfo engineResultInfo4 = mock();
+		when(engineResultInfo1.getRootDescriptor()).thenReturn(rootDescriptor1);
+		when(engineResultInfo2.getRootDescriptor()).thenReturn(rootDescriptor2);
+		when(engineResultInfo3.getRootDescriptor()).thenReturn(rootDescriptor3);
+		when(engineResultInfo4.getRootDescriptor()).thenReturn(rootDescriptor4);
+
+		@SuppressWarnings("serial")
+		Map<TestEngine, EngineResultInfo> engineResults = new LinkedHashMap<>() {
+			{
+				put(engine1, engineResultInfo1);
+				put(engine2, engineResultInfo2);
+				put(engine3, engineResultInfo3);
+				put(engine4, engineResultInfo4);
+			}
+		};
+
+		assertThat(engineResults.keySet()).containsExactly(engine1, engine2, engine3, engine4);
+
+		LauncherDiscoveryResult discoveryResult = new LauncherDiscoveryResult(engineResults, mock(), mock());
+		assertThat(discoveryResult.getTestEngines()).containsExactly(engine1, engine2, engine3, engine4);
+
+		LauncherDiscoveryResult withRetainedEngines = discoveryResult.withRetainedEngines(TestDescriptor::isTest);
+
+		assertThat(withRetainedEngines.getTestEngines()).containsExactly(engine1, engine4);
+	}
+
+	private static abstract class AbstractDummyEngine implements TestEngine {
+
+		@Override
+		public String getId() {
+			return getClass().getSimpleName();
+		}
+
+		@Override
+		public TestDescriptor discover(EngineDiscoveryRequest discoveryRequest, UniqueId uniqueId) {
+			throw new UnsupportedOperationException("discover");
+		}
+
+		@Override
+		public void execute(ExecutionRequest request) {
+			throw new UnsupportedOperationException("execute");
+		}
+	}
+
+	private static class DummyEngine1 extends AbstractDummyEngine {
+	}
+
+	private static class DummyEngine2 extends AbstractDummyEngine {
+	}
+
+	private static class DummyEngine3 extends AbstractDummyEngine {
+	}
+
+	private static class DummyEngine4 extends AbstractDummyEngine {
+	}
+
+}