diff --git a/CHANGELOG.md b/CHANGELOG.md
index aa2923fac..21b136f51 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5,6 +5,20 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](http://keepachangelog.com/)
 and this project adheres to [Semantic Versioning](http://semver.org/).
 
+
+## Unrealeased
+
+### Changed
+
+- App `title` and `sub_title` attributes can be set to any type https://github.com/Textualize/textual/issues/2521
+
+### Fixed
+
+- Fixed `ZeroDivisionError` in `resolve_fraction_unit` https://github.com/Textualize/textual/issues/2502
+- Fixed `TreeNode.expand` and `TreeNode.expand_all` not posting a `Tree.NodeExpanded` message https://github.com/Textualize/textual/issues/2535
+- Fixed `TreeNode.collapse` and `TreeNode.collapse_all` not posting a `Tree.NodeCollapsed` message https://github.com/Textualize/textual/issues/2535
+- Fixed `TreeNode.toggle` and `TreeNode.toggle_all` not posting a `Tree.NodeExpanded` or `Tree.NodeCollapsed` message https://github.com/Textualize/textual/issues/2535
+
 ## [0.24.1] - 2023-05-08
 
 ### Fixed
diff --git a/src/textual/_resolve.py b/src/textual/_resolve.py
index ddbdd1d5c..79a1a1e3e 100644
--- a/src/textual/_resolve.py
+++ b/src/textual/_resolve.py
@@ -143,7 +143,7 @@ def resolve_fraction_unit(
     resolved: list[Fraction | None] = [None] * len(resolve)
     remaining_fraction = Fraction(sum(scalar.value for scalar, _, _ in resolve))
 
-    while True:
+    while remaining_fraction > 0:
         remaining_space_changed = False
         resolve_fraction = Fraction(remaining_space, remaining_fraction)
         for index, (scalar, min_value, max_value) in enumerate(resolve):
@@ -166,7 +166,7 @@ def resolve_fraction_unit(
 
     return (
         Fraction(remaining_space, remaining_fraction)
-        if remaining_space
+        if remaining_space > 0
         else Fraction(1)
     )
 
diff --git a/src/textual/app.py b/src/textual/app.py
index 113a7a220..12f66cf04 100644
--- a/src/textual/app.py
+++ b/src/textual/app.py
@@ -316,6 +316,7 @@ class App(Generic[ReturnType], DOMNode):
         the name of the app if it doesn't.
 
         Assign a new value to this attribute to change the title.
+        The new value is always converted to string.
         """
 
         self.sub_title = self.SUB_TITLE if self.SUB_TITLE is not None else ""
@@ -328,6 +329,7 @@ class App(Generic[ReturnType], DOMNode):
         the file being worker on.
 
         Assign a new value to this attribute to change the sub-title.
+        The new value is always converted to string.
         """
 
         self._logger = Logger(self._log)
@@ -406,6 +408,14 @@ class App(Generic[ReturnType], DOMNode):
         self.set_class(self.dark, "-dark-mode")
         self.set_class(not self.dark, "-light-mode")
 
+    def validate_title(self, title: Any) -> str:
+        """Make sure the title is set to a string."""
+        return str(title)
+
+    def validate_sub_title(self, sub_title: Any) -> str:
+        """Make sure the sub-title is set to a string."""
+        return str(sub_title)
+
     @property
     def workers(self) -> WorkerManager:
         """The [worker](guide/workers/) manager.
diff --git a/src/textual/widgets/_tree.py b/src/textual/widgets/_tree.py
index aab6e9cc5..01cf2f180 100644
--- a/src/textual/widgets/_tree.py
+++ b/src/textual/widgets/_tree.py
@@ -207,6 +207,7 @@ class TreeNode(Generic[TreeDataType]):
         """
         self._expanded = True
         self._updates += 1
+        self._tree.post_message(Tree.NodeExpanded(self._tree, self))
         if expand_all:
             for child in self.children:
                 child._expand(expand_all)
@@ -239,6 +240,7 @@ class TreeNode(Generic[TreeDataType]):
         """
         self._expanded = False
         self._updates += 1
+        self._tree.post_message(Tree.NodeCollapsed(self._tree, self))
         if collapse_all:
             for child in self.children:
                 child._collapse(collapse_all)
@@ -1157,10 +1159,8 @@ class Tree(Generic[TreeDataType], ScrollView, can_focus=True):
             return
         if node.is_expanded:
             node.collapse()
-            self.post_message(self.NodeCollapsed(self, node))
         else:
             node.expand()
-            self.post_message(self.NodeExpanded(self, node))
 
     async def _on_click(self, event: events.Click) -> None:
         meta = event.style.meta
diff --git a/tests/test_app.py b/tests/test_app.py
index e529cfbd7..54bde8221 100644
--- a/tests/test_app.py
+++ b/tests/test_app.py
@@ -36,3 +36,33 @@ async def test_hover_update_styles():
         # We've hovered, so ensure the pseudoclass is present and background changed
         assert button.pseudo_classes == {"enabled", "hover"}
         assert button.styles.background != initial_background
+
+
+def test_setting_title():
+    app = MyApp()
+    app.title = None
+    assert app.title == "None"
+
+    app.title = ""
+    assert app.title == ""
+
+    app.title = 0.125
+    assert app.title == "0.125"
+
+    app.title = [True, False, 2]
+    assert app.title == "[True, False, 2]"
+
+
+def test_setting_sub_title():
+    app = MyApp()
+    app.sub_title = None
+    assert app.sub_title == "None"
+
+    app.sub_title = ""
+    assert app.sub_title == ""
+
+    app.sub_title = 0.125
+    assert app.sub_title == "0.125"
+
+    app.sub_title = [True, False, 2]
+    assert app.sub_title == "[True, False, 2]"
diff --git a/tests/test_resolve.py b/tests/test_resolve.py
index c36e1a406..202299747 100644
--- a/tests/test_resolve.py
+++ b/tests/test_resolve.py
@@ -1,4 +1,5 @@
 from fractions import Fraction
+from itertools import chain
 
 import pytest
 
@@ -122,3 +123,22 @@ def test_resolve_fraction_unit():
         Fraction(32),
         resolve_dimension="width",
     ) == Fraction(2)
+
+
+def test_resolve_issue_2502():
+    """Test https://github.com/Textualize/textual/issues/2502"""
+
+    widget = Widget()
+    widget.styles.width = "1fr"
+    widget.styles.min_width = 11
+
+    assert isinstance(
+        resolve_fraction_unit(
+            (widget.styles,),
+            Size(80, 24),
+            Size(80, 24),
+            Fraction(10),
+            resolve_dimension="width",
+        ),
+        Fraction,
+    )
diff --git a/tests/tree/test_tree_messages.py b/tests/tree/test_tree_messages.py
index ef742319a..bc55a7d81 100644
--- a/tests/tree/test_tree_messages.py
+++ b/tests/tree/test_tree_messages.py
@@ -78,6 +78,20 @@ async def test_tree_node_expanded_message() -> None:
         assert pilot.app.messages == [("NodeExpanded", "test-tree")]
 
 
+async def tree_node_expanded_by_code_message() -> None:
+    """Expanding a node via the API should result in an expanded message being posted."""
+    async with TreeApp().run_test() as pilot:
+        pilot.app.query_one(Tree).root.children[0].expand()
+        assert pilot.app.messages == [("NodeExpanded", "test-tree")]
+
+
+async def tree_node_all_expanded_by_code_message() -> None:
+    """Expanding all nodes via the API should result in expanded messages being posted."""
+    async with TreeApp().run_test() as pilot:
+        pilot.app.query_one(Tree).root.children[0].expand_all()
+        assert pilot.app.messages == [("NodeExpanded", "test-tree")]
+
+
 async def test_tree_node_collapsed_message() -> None:
     """Collapsing a node should result in a collapsed message being emitted."""
     async with TreeApp().run_test() as pilot:
@@ -89,6 +103,46 @@ async def test_tree_node_collapsed_message() -> None:
         ]
 
 
+async def tree_node_collapsed_by_code_message() -> None:
+    """Collapsing a node via the API should result in a collapsed message being posted."""
+    async with TreeApp().run_test() as pilot:
+        pilot.app.query_one(Tree).root.children[0].expand().collapse()
+        assert pilot.app.messages == [
+            ("NodeExpanded", "test-tree"),
+            ("NodeCollapsed", "test-tree"),
+        ]
+
+
+async def tree_node_all_collapsed_by_code_message() -> None:
+    """Collapsing all nodes via the API should result in collapsed messages being posted."""
+    async with TreeApp().run_test() as pilot:
+        pilot.app.query_one(Tree).root.children[0].expand_all().collapse_all()
+        assert pilot.app.messages == [
+            ("NodeExpanded", "test-tree"),
+            ("NodeCollapsed", "test-tree"),
+        ]
+
+
+async def tree_node_toggled_by_code_message() -> None:
+    """Toggling a node twice via the API should result in expanded and collapsed messages."""
+    async with TreeApp().run_test() as pilot:
+        pilot.app.query_one(Tree).root.children[0].toggle().toggle()
+        assert pilot.app.messages == [
+            ("NodeExpanded", "test-tree"),
+            ("NodeCollapsed", "test-tree"),
+        ]
+
+
+async def tree_node_all_toggled_by_code_message() -> None:
+    """Toggling all nodes twice via the API should result in expanded and collapsed messages."""
+    async with TreeApp().run_test() as pilot:
+        pilot.app.query_one(Tree).root.children[0].toggle_all().toggle_all()
+        assert pilot.app.messages == [
+            ("NodeExpanded", "test-tree"),
+            ("NodeCollapsed", "test-tree"),
+        ]
+
+
 async def test_tree_node_highlighted_message() -> None:
     """Highlighting a node should result in a highlighted message being emitted."""
     async with TreeApp().run_test() as pilot: