Migrate org.eclipse.core.tests.internal.runtime to JUnit 5

[HeikoKlare]

• Use JUnit 5 test annotation
• Remove obsolete assertions messages
• Migrate assertions to JUnit 5
• Replace Hamcrest assertions with AssertJ

Contributes to #903

[eclipse-platform-bot]

This pull request changes some projects for the first time in this development cycle.
Therefore the following files need a version increment:

runtime/tests/org.eclipse.core.tests.runtime/META-INF/MANIFEST.MF

An additional commit containing all the necessary changes was pushed to the top of this PR's branch. To obtain these changes (for example if you want to push more changes) either fetch from your fork or apply the git patch.

Git patch

From bfef1582de51a4fa898cdc19245a3d5ce75683bb Mon Sep 17 00:00:00 2001
From: Eclipse Platform Bot <platform-bot@eclipse.org>
Date: Tue, 30 Dec 2025 13:19:49 +0000
Subject: [PATCH] Version bump(s) for 4.39 stream


diff --git a/runtime/tests/org.eclipse.core.tests.runtime/META-INF/MANIFEST.MF b/runtime/tests/org.eclipse.core.tests.runtime/META-INF/MANIFEST.MF
index 2487c0c862..cac1f2b6c4 100644
--- a/runtime/tests/org.eclipse.core.tests.runtime/META-INF/MANIFEST.MF
+++ b/runtime/tests/org.eclipse.core.tests.runtime/META-INF/MANIFEST.MF
@@ -2,7 +2,7 @@ Manifest-Version: 1.0
 Bundle-ManifestVersion: 2
 Bundle-Name: Eclipse Core Tests Runtime
 Bundle-SymbolicName: org.eclipse.core.tests.runtime; singleton:=true
-Bundle-Version: 3.21.800.qualifier
+Bundle-Version: 3.21.900.qualifier
 Bundle-Activator: org.eclipse.core.tests.runtime.RuntimeTestsPlugin
 Bundle-Vendor: Eclipse.org
 Export-Package: org.eclipse.core.tests.internal.preferences,
-- 
2.52.0

Further information are available in Common Build Issues - Missing version increments.

[github-actions]

Test Results

 1 953 files  ±0   1 953 suites  ±0   1h 33m 4s ⏱️ + 9m 6s
 4 745 tests ±0   4 721 ✅ ±0   24 💤 ±0  0 ❌ ±0 
14 235 runs  ±0  14 053 ✅ ±0  182 💤 ±0  0 ❌ ±0 

Results for commit 875af07. ± Comparison against base commit 3b0c3f3.

♻️ This comment has been updated with latest results.