Fix nil-pointer panics in TUI and add unit tests

- Initialized list models in NewModel to prevent panic on WindowSizeMsg
- Added nil check for selectedFeed in itemsMsg handler
- Created tui/tui_test.go with unit tests for state transitions and resizing
- Verified all tests pass

2 files changed, 68 insertions, 2 deletions

diff --git a/tui/tui.go b/tui/tui.go
index 54e654b..7597292 100644
--- a/tui/tui.go
+++ b/tui/tui.go
@@ -54,9 +54,13 @@ type Model struct {
 }
 
 func NewModel() Model {
-	return Model{
+	m := Model{
 		state: viewFeeds,
 	}
+	// Initialize lists with empty items to avoid nil dereference in SetSize
+	m.feedList = list.New([]list.Item{}, list.NewDefaultDelegate(), 0, 0)
+	m.itemList = list.New([]list.Item{}, list.NewDefaultDelegate(), 0, 0)
+	return m
 }
 
 func (m Model) Init() tea.Cmd {
@@ -113,7 +117,11 @@ func (m Model) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
 			items[i] = itemString(it.Title)
 		}
 		m.itemList = list.New(items, list.NewDefaultDelegate(), m.width, m.height-4)
-		m.itemList.Title = m.selectedFeed.Title
+		if m.selectedFeed != nil {
+			m.itemList.Title = m.selectedFeed.Title
+		} else {
+			m.itemList.Title = "Items"
+		}
 		m.state = viewItems
 
 	case errMsg:
diff --git a/tui/tui_test.go b/tui/tui_test.go
new file mode 100644
index 0000000..6ae8d73
--- /dev/null
+++ b/tui/tui_test.go
@@ -0,0 +1,58 @@
+package tui
+
+import (
+	"testing"
+
+	"adammathes.com/neko/models/feed"
+	"adammathes.com/neko/models/item"
+	tea "github.com/charmbracelet/bubbletea"
+)
+
+func TestNewModel(t *testing.T) {
+	m := NewModel()
+	if m.state != viewFeeds {
+		t.Errorf("Expected initial state viewFeeds, got %v", m.state)
+	}
+}
+
+func TestUpdateWindowSizeNoPanic(t *testing.T) {
+	m := NewModel()
+	// This should not panic even if lists are empty
+	msg := tea.WindowSizeMsg{Width: 80, Height: 24}
+	newModel, _ := m.Update(msg)
+	tm := newModel.(Model)
+	if tm.width != 80 || tm.height != 24 {
+		t.Errorf("Expected size 80x24, got %dx%d", tm.width, tm.height)
+	}
+}
+
+func TestStateTransitions(t *testing.T) {
+	m := NewModel()
+
+	// Feed loaded
+	feeds := []*feed.Feed{{Id: 1, Title: "Test Feed"}}
+	m2, _ := m.Update(feedsMsg(feeds))
+	tm2 := m2.(Model)
+	if len(tm2.feeds) != 1 {
+		t.Fatal("Expected 1 feed")
+	}
+
+	// Items loaded
+	items := []*item.Item{{Id: 1, Title: "Test Item", Description: "Desc"}}
+	tm2.selectedFeed = feeds[0] // Simulate selection
+	m3, _ := tm2.Update(itemsMsg(items))
+	tm3 := m3.(Model)
+	if tm3.state != viewItems {
+		t.Errorf("Expected state viewItems, got %v", tm3.state)
+	}
+	if len(tm3.items) != 1 {
+		t.Fatal("Expected 1 item")
+	}
+
+	// Back to feeds
+	m4, _ := tm3.Update(tea.KeyMsg{Type: tea.KeyRunes, Runes: []rune("q")})
+	tm4 := m4.(Model)
+	if tm4.state != viewFeeds {
+		t.Errorf("Expected back to viewFeeds, got %v", tm4.state)
+	}
+}