diff --git a/.github/workflows/change-coverage.yml b/.github/workflows/change-coverage.yml
new file mode 100644
index 000000000..7e32465ed
--- /dev/null
+++ b/.github/workflows/change-coverage.yml
@@ -0,0 +1,48 @@
+name: Execute tests
+on:
+  workflow_call:
+    inputs:
+      basepath:
+        required: false
+        type: string
+      os:
+        required: true
+        type: string
+      workpath:
+        required: true
+        type: string
+
+jobs:
+  change-coverage:
+    runs-on: ubuntu-latest
+    name: Change coverage
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+
+      - uses: actions/setup-python@v5
+        with:
+          python-version: "3.11"
+          architecture: x64
+
+      - uses: Gr1N/setup-poetry@v8
+
+      - name: Check system dependencies
+        run: make doctor
+
+      - uses: actions/cache@v4
+        with:
+          path: .venv
+          key: ${{ runner.os }}-poetry-${{ hashFiles('poetry.lock') }}
+
+      - name: Install project dependencies
+        run: make install
+      
+      - name: Check coverage
+        run: |
+          TEST_INTEGRATION=true poetry run pytest doorstop --doctest-modules --cov=doorstop --cov-report=xml --cov-report=term-missing
+          git fetch origin develop:develop
+          # TEST_INTEGRATION=true poetry run diff-cover ./coverage.xml --fail-under=100 --compare-branch=develop
+          TEST_INTEGRATION=true poetry run diff-cover ./coverage.xml --fail-under=100 --compare-branch=$(git for-each-ref --sort=-committerdate refs/heads/develop | cut -f 1 -d ' ')
diff --git a/.github/workflows/execute-tests.yml b/.github/workflows/execute-tests.yml
index 9f80c5ca6..28836e678 100644
--- a/.github/workflows/execute-tests.yml
+++ b/.github/workflows/execute-tests.yml
@@ -27,7 +27,7 @@ jobs:
 
     steps:
       - name: Checkout
-        uses: actions/checkout@v2
+        uses: actions/checkout@v4
 
       - name: Change path on Windows
         if: ${{ inputs.os == 'windows-latest' }}
@@ -38,7 +38,7 @@ jobs:
           mkdir -p ${{ inputs.workpath }}
           mv $env:GITHUB_WORKSPACE\* ${{ inputs.workpath }}\ -Force
 
-      - uses: actions/setup-python@v2
+      - uses: actions/setup-python@v5
         with:
           python-version: ${{ matrix.python-version }}
           architecture: x64
@@ -48,7 +48,7 @@ jobs:
       - name: Check system dependencies
         run: make doctor
 
-      - uses: actions/cache@v2
+      - uses: actions/cache@v4
         with:
           path: .venv
           key: ${{ runner.os }}-poetry-${{ hashFiles('poetry.lock') }}
@@ -60,7 +60,7 @@ jobs:
       # very slow. Especially any client/server tests seems to be problematic.
       # This is a simple attempt to re-run the tests up to three times if they
       # fail. Does not add any execution time if successful.
-      - uses: Wandalen/wretry.action@v1.0.20
+      - uses: Wandalen/wretry.action@v1.4.4
         name: Run tests
         with:
           command: make test
diff --git a/.github/workflows/test-linux.yml b/.github/workflows/test-linux.yml
index 4bcfc716b..6514a62d6 100644
--- a/.github/workflows/test-linux.yml
+++ b/.github/workflows/test-linux.yml
@@ -6,6 +6,11 @@ on:
     branches: [ develop ]
 
 jobs:
+  Coverage:
+    uses: ./.github/workflows/change-coverage.yml
+    with:
+      os: "ubuntu-latest"
+      workpath: "/home/runner/work/doorstop/doorstop"
   Test:
     uses: ./.github/workflows/execute-tests.yml
     with:
diff --git a/.gitignore b/.gitignore
index 2650cc9a7..15824409f 100644
--- a/.gitignore
+++ b/.gitignore
@@ -11,6 +11,7 @@ Icon*
 # Temporary virtual environment files
 /.cache/
 /.venv/
+/.python-version
 
 # Temporary server files
 .env
diff --git a/Makefile b/Makefile
index 33d818a7e..e09db7e4e 100644
--- a/Makefile
+++ b/Makefile
@@ -116,7 +116,7 @@ test-cover: install
 # Run first to generate coverage data current code.
 	TEST_INTEGRATION=true poetry run pytest doorstop --doctest-modules --cov=doorstop --cov-report=xml --cov-report=term-missing
 # Run second to generate coverage data for the code in the develop branch.
-	TEST_INTEGRATION=true diff-cover ./coverage.xml --compare-branch=$(shell git for-each-ref --sort=-committerdate refs/heads/develop | cut -f 1 -d ' ')
+	TEST_INTEGRATION=true poetry run diff-cover ./coverage.xml --fail-under=100 --compare-branch=$(shell git for-each-ref --sort=-committerdate refs/heads/develop | cut -f 1 -d ' ')
 
 .PHONY: read-coverage
 read-coverage:
diff --git a/doorstop/cli/tests/test_all.py b/doorstop/cli/tests/test_all.py
index 05c87983a..60afd97d9 100644
--- a/doorstop/cli/tests/test_all.py
+++ b/doorstop/cli/tests/test_all.py
@@ -21,6 +21,7 @@
 )
 from doorstop.core.builder import _clear_tree
 from doorstop.core.document import Document
+from doorstop.core.tests.helpers import on_error_with_retry
 
 REQ_COUNT = 23
 ALL_COUNT = 55
@@ -36,7 +37,7 @@ def setUp(self):
     def tearDown(self):
         os.chdir(self.cwd)
         if os.path.exists(self.temp):
-            shutil.rmtree(self.temp)
+            shutil.rmtree(self.temp, onerror=on_error_with_retry)
 
 
 class MockTestCase(TempTestCase):
@@ -62,7 +63,7 @@ def setUp(self):
     def tearDown(self):
         super().tearDown()
         os.chdir(self.cwd)
-        shutil.rmtree(self.temp)
+        shutil.rmtree(self.temp, onerror=on_error_with_retry)
 
     def test_main(self):
         """Verify 'doorstop' can be called."""
diff --git a/doorstop/core/publishers/base.py b/doorstop/core/publishers/base.py
index 056ae4e3f..e34d0f0bb 100644
--- a/doorstop/core/publishers/base.py
+++ b/doorstop/core/publishers/base.py
@@ -320,22 +320,23 @@ def get_document_attributes(obj, is_html=False, extensions=None):
     except AttributeError:
         attribute_defaults = None
     if attribute_defaults:
-        if "name" in attribute_defaults["doc"]:
-            # Name should only be set if it is not empty.
-            if attribute_defaults["doc"]["name"] != "":
-                doc_attributes["name"] = attribute_defaults["doc"]["name"]
-        if "title" in attribute_defaults["doc"]:
-            doc_attributes["title"] = attribute_defaults["doc"]["title"]
-        if "ref" in attribute_defaults["doc"]:
-            doc_attributes["ref"] = attribute_defaults["doc"]["ref"]
-        if "by" in attribute_defaults["doc"]:
-            doc_attributes["by"] = attribute_defaults["doc"]["by"]
-        if "major" in attribute_defaults["doc"]:
-            doc_attributes["major"] = attribute_defaults["doc"]["major"]
-        if "minor" in attribute_defaults["doc"]:
-            doc_attributes["minor"] = attribute_defaults["doc"]["minor"]
-        if "copyright" in attribute_defaults["doc"]:
-            doc_attributes["copyright"] = attribute_defaults["doc"]["copyright"]
+        if "doc" in attribute_defaults:
+            if "name" in attribute_defaults["doc"]:
+                # Name should only be set if it is not empty.
+                if attribute_defaults["doc"]["name"] != "":
+                    doc_attributes["name"] = attribute_defaults["doc"]["name"]
+            if "title" in attribute_defaults["doc"]:
+                doc_attributes["title"] = attribute_defaults["doc"]["title"]
+            if "ref" in attribute_defaults["doc"]:
+                doc_attributes["ref"] = attribute_defaults["doc"]["ref"]
+            if "by" in attribute_defaults["doc"]:
+                doc_attributes["by"] = attribute_defaults["doc"]["by"]
+            if "major" in attribute_defaults["doc"]:
+                doc_attributes["major"] = attribute_defaults["doc"]["major"]
+            if "minor" in attribute_defaults["doc"]:
+                doc_attributes["minor"] = attribute_defaults["doc"]["minor"]
+            if "copyright" in attribute_defaults["doc"]:
+                doc_attributes["copyright"] = attribute_defaults["doc"]["copyright"]
     # Check output format. If html we need go convert from markdown.
     if is_html:
         # Only convert title and copyright.
diff --git a/doorstop/core/publishers/tests/test_publisher_html.py b/doorstop/core/publishers/tests/test_publisher_html.py
index 67f9d55f9..9f83c5923 100644
--- a/doorstop/core/publishers/tests/test_publisher_html.py
+++ b/doorstop/core/publishers/tests/test_publisher_html.py
@@ -5,6 +5,7 @@
 # pylint: disable=unused-argument,protected-access
 
 import os
+import stat
 import unittest
 from secrets import token_hex
 from shutil import rmtree
@@ -22,6 +23,7 @@
     MockDocument,
     MockItem,
 )
+from doorstop.core.tests.helpers import on_error_with_retry
 from doorstop.core.types import UID
 
 
@@ -37,7 +39,7 @@ def setUp(self):
     @classmethod
     def tearDownClass(cls):
         """Remove test folder."""
-        rmtree("mock_%s" % __name__)
+        rmtree("mock_%s" % __name__, onerror=on_error_with_retry)
 
     @patch("os.path.isdir", Mock(side_effect=[False, False, False, False]))
     @patch("os.makedirs")
diff --git a/doorstop/core/publishers/tests/test_publisher_html_doc.py b/doorstop/core/publishers/tests/test_publisher_html_doc.py
index 8104defa4..3a947debc 100644
--- a/doorstop/core/publishers/tests/test_publisher_html_doc.py
+++ b/doorstop/core/publishers/tests/test_publisher_html_doc.py
@@ -5,6 +5,7 @@
 # pylint: disable=unused-argument,protected-access
 
 import os
+import stat
 import unittest
 from secrets import token_hex
 from shutil import rmtree
@@ -14,6 +15,7 @@
 from doorstop.core.builder import build
 from doorstop.core.publishers.tests.helpers import HTML_TEMPLATE_WALK, getWalk
 from doorstop.core.tests import ROOT, MockDataMixIn
+from doorstop.core.tests.helpers import on_error_with_retry
 
 
 class TestPublisherFullDocument(MockDataMixIn, unittest.TestCase):
@@ -44,7 +46,7 @@ def setUp(self):
     @classmethod
     def tearDownClass(cls):
         """Remove test folder."""
-        rmtree("mock_%s" % __name__)
+        rmtree("mock_%s" % __name__, onerror=on_error_with_retry)
 
     def test_publish_html_tree_copies_assets(self):
         """Verify that html assets are published when publishing a tree."""
diff --git a/doorstop/core/publishers/tests/test_publisher_latex_doc.py b/doorstop/core/publishers/tests/test_publisher_latex_doc.py
index dc0c551dd..da84a1f96 100644
--- a/doorstop/core/publishers/tests/test_publisher_latex_doc.py
+++ b/doorstop/core/publishers/tests/test_publisher_latex_doc.py
@@ -5,6 +5,7 @@
 # pylint: disable=unused-argument,protected-access
 
 import os
+import stat
 import unittest
 from secrets import token_hex
 from shutil import rmtree
@@ -21,6 +22,7 @@
     YAML_LATEX_ONLY_REF,
 )
 from doorstop.core.tests import ROOT, MockDataMixIn, MockDocument
+from doorstop.core.tests.helpers import on_error_with_retry
 
 
 class TestPublisherFullDocument(MockDataMixIn, unittest.TestCase):
@@ -58,7 +60,7 @@ def setUp(self):
     @classmethod
     def tearDownClass(cls):
         """Remove test folder."""
-        rmtree("mock_%s" % __name__)
+        rmtree("mock_%s" % __name__, onerror=on_error_with_retry)
 
     def test_publish_latex_tree_copies_assets(self):
         """Verify that LaTeX assets are published when publishing a tree."""
diff --git a/doorstop/core/publishers/tests/test_publisher_markdown.py b/doorstop/core/publishers/tests/test_publisher_markdown.py
index aae1d30a2..88e637ff5 100644
--- a/doorstop/core/publishers/tests/test_publisher_markdown.py
+++ b/doorstop/core/publishers/tests/test_publisher_markdown.py
@@ -5,6 +5,7 @@
 # pylint: disable=unused-argument,protected-access
 
 import os
+import stat
 import unittest
 from secrets import token_hex
 from shutil import rmtree
@@ -20,6 +21,7 @@
     MockItem,
     MockItemAndVCS,
 )
+from doorstop.core.tests.helpers import on_error_with_retry
 
 
 class TestModule(MockDataMixIn, unittest.TestCase):
@@ -35,7 +37,7 @@ def setUp(self):
     def tearDownClass(cls):
         """Remove test folder."""
         if os.path.exists("mock_%s" % __name__):
-            rmtree("mock_%s" % __name__)
+            rmtree("mock_%s" % __name__, onerror=on_error_with_retry)
 
     def test_lines_markdown_item(self):
         """Verify Markdown can be published from an item."""
diff --git a/doorstop/core/publishers/tests/test_publisher_markdown_doc.py b/doorstop/core/publishers/tests/test_publisher_markdown_doc.py
index 247f89eea..0c1af1b41 100644
--- a/doorstop/core/publishers/tests/test_publisher_markdown_doc.py
+++ b/doorstop/core/publishers/tests/test_publisher_markdown_doc.py
@@ -5,6 +5,7 @@
 # pylint: disable=unused-argument,protected-access
 
 import os
+import stat
 import unittest
 from secrets import token_hex
 from shutil import rmtree
@@ -13,6 +14,7 @@
 from doorstop.core.builder import build
 from doorstop.core.publishers.tests.helpers import getWalk
 from doorstop.core.tests import ROOT, MockDataMixIn, MockDocument
+from doorstop.core.tests.helpers import on_error_with_retry
 
 
 class TestPublisherFullDocument(MockDataMixIn, unittest.TestCase):
@@ -40,7 +42,7 @@ def setUp(self):
     @classmethod
     def tearDownClass(cls):
         """Remove test folder."""
-        rmtree("mock_%s" % __name__)
+        rmtree("mock_%s" % __name__, onerror=on_error_with_retry)
 
     def test_publish_markdown_tree_copies_assets(self):
         """Verify that markdown assets are published when publishing a tree."""
diff --git a/doorstop/core/publishers/tests/test_publisher_text.py b/doorstop/core/publishers/tests/test_publisher_text.py
index 9b9c632e1..0223ae8a8 100644
--- a/doorstop/core/publishers/tests/test_publisher_text.py
+++ b/doorstop/core/publishers/tests/test_publisher_text.py
@@ -5,6 +5,7 @@
 # pylint: disable=unused-argument,protected-access
 
 import os
+import stat
 import unittest
 from secrets import token_hex
 from shutil import rmtree
@@ -13,6 +14,7 @@
 from doorstop.core import publisher
 from doorstop.core.publishers.tests.helpers import getLines
 from doorstop.core.tests import MockDataMixIn, MockItemAndVCS
+from doorstop.core.tests.helpers import on_error_with_retry
 
 
 class TestModule(MockDataMixIn, unittest.TestCase):
@@ -28,7 +30,7 @@ def setUp(self):
     def tearDownClass(cls):
         """Remove test folder."""
         if os.path.exists("mock_%s" % __name__):
-            rmtree("mock_%s" % __name__)
+            rmtree("mock_%s" % __name__, onerror=on_error_with_retry)
 
     def test_lines_text_item(self):
         """Verify text can be published from an item."""
diff --git a/doorstop/core/template.py b/doorstop/core/template.py
index 709946899..0da6681cf 100644
--- a/doorstop/core/template.py
+++ b/doorstop/core/template.py
@@ -53,7 +53,17 @@ def get_template(obj, path, ext, template):
     output_dir = path
 
     if is_tree(obj):
-        document_template = obj.documents[0].template
+        document_template = None
+        template_count = 0
+        for each in obj.documents:
+            if each.template:
+                document_template = each.template
+                template_count += 1
+        if template_count > 1:
+            raise common.DoorstopError(
+                """Multiple templates found in tree. Please specify a single template for the tree.
+I.e., only one of the documents in the tree should have a template folder."""
+            )
     else:
         document_template = obj.template
 
diff --git a/doorstop/core/tests/helpers.py b/doorstop/core/tests/helpers.py
index 1a80c4757..8ac1c4426 100644
--- a/doorstop/core/tests/helpers.py
+++ b/doorstop/core/tests/helpers.py
@@ -3,7 +3,10 @@
 
 """Unit test helper functions to reduce code duplication."""
 from logging import NullHandler
+from os import chmod
 from shutil import copytree
+from stat import S_IWRITE
+from time import sleep
 from typing import List
 
 from doorstop.core.builder import build
@@ -33,3 +36,29 @@ def build_expensive_tree(obj):
     # Build a tree.
     copytree(ROOT, obj.datapath)
     obj.mock_tree = build(cwd=obj.datapath, root=obj.datapath, request_next_number=None)
+
+
+def on_error_with_retry(func, path, exc_info, retries=60):
+    """Define a separate function to handle errors for rmtree.
+
+    This callback function is used to retry rmtree operations
+    that fail for up to 60 seconds. This is necessary because
+    Windows does not always release file handles immediately,
+    and the rmtree operation can fail.
+    """
+    if retries > 0:
+        # Change the file permissions
+        chmod(path, S_IWRITE)
+        # Sleep for 1 seconds to wait for the race condition to resolve
+        sleep(1)
+        try:
+            # Try the operation again
+            func(path)
+        # pylint: disable=broad-except
+        except Exception as e:
+            # If an error occurs, recurse with one fewer retry available
+            print(f"Retry {5 - retries} failed for {path}, error: {e}. Retrying...")
+            on_error_with_retry(func, path, exc_info, retries - 1)
+    else:
+        # If no retries are left, raise an exception or handle the final failure case
+        print(f"Failed to remove {path} after multiple retries.")
diff --git a/doorstop/core/tests/test_all.py b/doorstop/core/tests/test_all.py
index 5030ad2dc..155c325aa 100644
--- a/doorstop/core/tests/test_all.py
+++ b/doorstop/core/tests/test_all.py
@@ -29,6 +29,7 @@
     SYS,
     DocumentNoSkip,
 )
+from doorstop.core.tests.helpers import on_error_with_retry
 from doorstop.core.vcs import mockvcs
 
 
@@ -387,7 +388,7 @@ def setUp(self):
 
     def tearDown(self):
         os.chdir(self.cwd)
-        shutil.rmtree(self.temp)
+        shutil.rmtree(self.temp, onerror=on_error_with_retry)
 
     def test_import_yml(self):
         """Verify items can be imported from a YAML file."""
@@ -521,7 +522,7 @@ def setUp(self):
         self.temp = tempfile.mkdtemp()
 
     def tearDown(self):
-        shutil.rmtree(self.temp)
+        shutil.rmtree(self.temp, onerror=on_error_with_retry)
 
     def test_export_yml(self):
         """Verify a document can be exported as a YAML file."""
@@ -577,7 +578,7 @@ def setUp(self):
 
     def tearDown(self):
         if os.path.exists(self.temp):
-            shutil.rmtree(self.temp)
+            shutil.rmtree(self.temp, onerror=on_error_with_retry)
 
     def test_publish_html(self):
         """Verify an HTML file can be created."""
diff --git a/doorstop/core/tests/test_publisher.py b/doorstop/core/tests/test_publisher.py
index cdcca6893..064993d75 100644
--- a/doorstop/core/tests/test_publisher.py
+++ b/doorstop/core/tests/test_publisher.py
@@ -14,6 +14,7 @@
 from doorstop.core import publisher
 from doorstop.core.builder import build
 from doorstop.core.tests import EMPTY, ROOT, MockDataMixIn
+from doorstop.core.tests.helpers import on_error_with_retry
 
 
 class TestModule(MockDataMixIn, unittest.TestCase):
@@ -40,7 +41,7 @@ def setUp(self):
     def tearDownClass(cls):
         """Remove test folder."""
         if os.path.exists("mock_%s" % __name__):
-            rmtree("mock_%s" % __name__)
+            rmtree("mock_%s" % __name__, onerror=on_error_with_retry)
 
     def test_publish_document_unknown(self):
         """Verify an exception is raised when publishing unknown formats."""
diff --git a/doorstop/core/tests/test_template.py b/doorstop/core/tests/test_template.py
index 937c58f70..46e335292 100644
--- a/doorstop/core/tests/test_template.py
+++ b/doorstop/core/tests/test_template.py
@@ -5,7 +5,6 @@
 # pylint: disable=unused-argument,protected-access
 
 import os
-import stat
 import unittest
 from pathlib import Path
 from secrets import token_hex
@@ -17,7 +16,7 @@
 from doorstop.core.builder import build
 from doorstop.core.publishers.tests.helpers import HTML_TEMPLATE_WALK, getWalk
 from doorstop.core.tests import ROOT, MockDataMixIn
-from doorstop.core.tests.helpers import build_expensive_tree
+from doorstop.core.tests.helpers import build_expensive_tree, on_error_with_retry
 
 
 class TestTemplate(MockDataMixIn, unittest.TestCase):
@@ -44,10 +43,7 @@ def setUpClass(cls):
     @classmethod
     def tearDownClass(cls):
         """Remove test folder."""
-        rmtree(
-            cls.testdir,
-            onerror=lambda func, path, _: (os.chmod(path, stat.S_IWRITE), func(path)),
-        )
+        rmtree(cls.testdir, onerror=on_error_with_retry)
 
     def test_standard_html_doc(self):
         """Verify that default html template is selected if no template is given and input is a document."""
@@ -147,6 +143,29 @@ def test_html_tree_with_custom_template(self):
         walk = getWalk(self.dirpath)
         self.assertEqual(expected_walk, walk)
 
+    def test_html_tree_with_multiple_template(self):
+        """Verify that a document tree with multiple custom html template throws an error."""
+        # This test MUST use the expensive tree since it changes the document content
+        # in the source tree otherwise!
+        build_expensive_tree(self)
+
+        # Check that only custom template is published.
+        os.makedirs(self.dirpath)
+        # Create a custom template folder.
+        doc_path = self.mock_tree.documents[0].path
+        os.mkdir(os.path.join(doc_path, "template"))
+        Path(os.path.join(doc_path, "template", "custom_css.css")).touch()
+        # Create another custom template folder.
+        doc_path = self.mock_tree.documents[1].path
+        os.mkdir(os.path.join(doc_path, "template"))
+        Path(os.path.join(doc_path, "template", "custom_css.css")).touch()
+
+        # Act
+        with self.assertRaises(DoorstopError):
+            _, _ = template.get_template(
+                self.mock_tree, self.dirpath, ".html", "custom_css"
+            )
+
     def test_html_doc_with_custom_template(self):
         """Verify that a custom html template is used correctly."""
         # This test MUST use the expensive tree since it changes the document content