diff --git a/.github/workflows/source-platform-smoke.yml b/.github/workflows/source-platform-smoke.yml
index f2759aa..2b7423c 100644
--- a/.github/workflows/source-platform-smoke.yml
+++ b/.github/workflows/source-platform-smoke.yml
@@ -54,7 +54,7 @@ jobs:
       - name: Install Python deps (CI subset)
         run: |
           python -m pip install --upgrade pip
-          python -m pip install "PySide6>=6.5.0" "PyMuPDF>=1.23.0" "pikepdf>=8.0.0" "pytesseract>=0.3.10" "Pillow>=10.0.0" "python-docx>=1.1.0" "chardet>=5.0.0" "rapidfuzz>=3.0.0" pytest pytest-subtests ruff
+          python -m pip install "PySide6>=6.5.0" "PyMuPDF>=1.23.0" "pikepdf>=8.0.0" "pytesseract>=0.3.10" "Pillow>=10.0.0" "python-docx>=1.1.0" "chardet>=5.0.0" "rapidfuzz>=3.0.0" "tomli>=2.0; python_version < '3.11'" pytest pytest-subtests ruff
 
       - name: Run ruff linting check
         run: |
diff --git a/tests/test_metadata.py b/tests/test_metadata.py
index 5b139c0..d4da4f7 100644
--- a/tests/test_metadata.py
+++ b/tests/test_metadata.py
@@ -4,11 +4,15 @@
 
 import json
 import re
-import tomllib
 import xml.etree.ElementTree as ET
 from pathlib import Path
 from PIL import Image
 
+try:
+    import tomllib
+except ModuleNotFoundError:  # Python 3.10
+    import tomli as tomllib
+
 ROOT = Path(__file__).resolve().parents[1]
 
 
@@ -285,8 +289,8 @@ def test_ci_workflow_integrity():
     assert "ubuntu-latest" in content
     assert "macos-latest" in content
     assert "windows-latest" in content
-    assert "actions/checkout@v4" in content
-    assert "actions/setup-python@v5" in content
+    assert re.search(r"actions/checkout@v\d+", content)
+    assert re.search(r"actions/setup-python@v\d+", content)
     assert "pytest" in content
     assert "concurrency:" in content
     assert "cancel-in-progress: true" in content
diff --git a/tests/test_pdf_collection.py b/tests/test_pdf_collection.py
index 8c9de2c..a1f2653 100644
--- a/tests/test_pdf_collection.py
+++ b/tests/test_pdf_collection.py
@@ -20,6 +20,34 @@
 )
 
 
+@pytest.fixture(scope="session")
+def collection_app():
+    """Keep Qt alive until every collection dialog has been destroyed."""
+    from PySide6.QtWidgets import QApplication
+
+    return QApplication.instance() or QApplication([])
+
+
+@pytest.fixture
+def collection_dialog_factory(collection_app):
+    from PySide6.QtCore import QCoreApplication, QEvent
+    from gui.dialogs.collection_export_dialog import CollectionExportDialog
+
+    dialogs = []
+
+    def create(**kwargs):
+        dialog = CollectionExportDialog(None, **kwargs)
+        dialogs.append(dialog)
+        return dialog
+
+    yield create
+    for dialog in dialogs:
+        dialog.close()
+        dialog.deleteLater()
+    QCoreApplication.sendPostedEvents(None, QEvent.Type.DeferredDelete)
+    collection_app.processEvents()
+
+
 @pytest.fixture
 def make_pdf(tmp_path):
     """Erzeugt eine Test-PDF mit angegebener Seitenzahl."""
@@ -176,17 +204,13 @@ def test_export_collection_all_files_missing(tmp_path):
     assert not out_pdf.exists()
 
 
-def test_dialog_reorder_and_filter(make_pdf):
+def test_dialog_reorder_and_filter(make_pdf, collection_dialog_factory):
     from PySide6.QtCore import Qt
-    from PySide6.QtWidgets import QApplication
-    from gui.dialogs.collection_export_dialog import CollectionExportDialog
-
-    _ = QApplication.instance() or QApplication([])
 
     pdf1 = make_pdf("alpha.pdf", pages=1)
     pdf2 = make_pdf("beta.pdf", pages=1)
 
-    dialog = CollectionExportDialog(None, initial_documents=[pdf1, pdf2])
+    dialog = collection_dialog_factory(initial_documents=[pdf1, pdf2])
     assert dialog._list_widget.count() == 2
 
     # Zweites Item auswählen und nach oben schieben
@@ -207,17 +231,14 @@ def test_dialog_reorder_and_filter(make_pdf):
     dialog.close()
 
 
-def test_dialog_export_execution(monkeypatch, tmp_path, make_pdf):
-    from PySide6.QtWidgets import QApplication, QFileDialog, QMessageBox
-    from gui.dialogs.collection_export_dialog import CollectionExportDialog
-
-    _ = QApplication.instance() or QApplication([])
+def test_dialog_export_execution(monkeypatch, tmp_path, make_pdf, collection_dialog_factory):
+    from PySide6.QtWidgets import QFileDialog, QMessageBox
 
     p1 = make_pdf("part1.pdf", pages=2)
     p2 = make_pdf("part2.pdf", pages=2)
     out_target = tmp_path / "gui_sammel.pdf"
 
-    dialog = CollectionExportDialog(None, initial_documents=[p1, p2], current_theme="Projekt")
+    dialog = collection_dialog_factory(initial_documents=[p1, p2], current_theme="Projekt")
 
     # Mocke Dateidialog und Nachfrage zum Öffnen
     monkeypatch.setattr(
diff --git a/tests/test_security_license_contract.py b/tests/test_security_license_contract.py
index ed48644..9b22921 100644
--- a/tests/test_security_license_contract.py
+++ b/tests/test_security_license_contract.py
@@ -15,10 +15,14 @@
 
 import os
 import re
-import tomllib
 import unittest
 from pathlib import Path
 
+try:
+    import tomllib
+except ModuleNotFoundError:  # Python 3.10
+    import tomli as tomllib
+
 ROOT = Path(__file__).resolve().parents[1]