diff --git a/internal/render/tui/alerts/alerts_test.go b/internal/render/tui/alerts/alerts_test.go
new file mode 100644
index 0000000..e2754cc
--- /dev/null
+++ b/internal/render/tui/alerts/alerts_test.go
@@ -0,0 +1,192 @@
+package alerts
+
+import (
+	"image/color"
+	"testing"
+	"time"
+
+	"charm.land/lipgloss/v2"
+	"github.com/mabd-dev/reposcan/internal/theme"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func testTheme() theme.Theme {
+	return theme.Theme{
+		Colors: theme.ColorScheme{
+			Foreground: lipgloss.Color("#ffffff"),
+			Error:      lipgloss.Color("#ff0000"),
+			Warning:    lipgloss.Color("#ffff00"),
+			Info:       lipgloss.Color("#0000ff"),
+			Border:     lipgloss.Color("#888888"),
+		},
+	}
+}
+
+func TestAlertLifecycle(t *testing.T) {
+	model := New(testTheme())
+
+	model, cmd := model.Update(AddAlertMsg{Msg: Alert{Title: "First"}})
+	require.NotNil(t, cmd)
+	model, cmd = model.Update(AddAlertMsg{Msg: Alert{Title: "Second"}})
+	assert.Nil(t, cmd)
+	require.Len(t, model.alerts, 2)
+
+	for range maxTicks - 1 {
+		model, cmd = model.Update(TickMsg{})
+	}
+	require.Len(t, model.alerts, 2)
+	assert.NotNil(t, cmd)
+
+	model, cmd = model.Update(TickMsg{})
+	require.Len(t, model.alerts, 1)
+	assert.Equal(t, "Second", model.alerts[0].Title)
+	assert.NotNil(t, cmd)
+
+	for range maxTicks {
+		model, cmd = model.Update(TickMsg{})
+	}
+	assert.Empty(t, model.alerts)
+	assert.Nil(t, cmd)
+
+	model, cmd = model.Update(TickMsg{})
+	assert.Empty(t, model.alerts)
+	assert.Nil(t, cmd)
+}
+
+func TestUpdateIgnoresUnknownMessages(t *testing.T) {
+	model := New(testTheme())
+	model, _ = model.Update(AddAlertMsg{Msg: Alert{Title: "Keep me"}})
+
+	updated, cmd := model.Update(struct{}{})
+
+	assert.Equal(t, model, updated)
+	assert.Nil(t, cmd)
+}
+
+func TestAlertStatesPositionsAndHidesOverflow(t *testing.T) {
+	model := New(testTheme())
+	model, _ = model.Update(AddAlertMsg{Msg: Alert{Message: "First"}})
+	model, _ = model.Update(AddAlertMsg{Msg: Alert{Message: "Second"}})
+	const totalWidth = 40
+
+	unconstrained := model.AlertStates(totalWidth, 100)
+	require.Len(t, unconstrained, 2)
+	firstHeight := lipgloss.Height(unconstrained[0].AlertView)
+
+	states := model.AlertStates(totalWidth, firstHeight)
+	require.Len(t, states, 2)
+	for _, state := range states {
+		assert.Equal(t, totalWidth, state.X+lipgloss.Width(state.AlertView))
+	}
+	assert.Equal(t, 0, states[0].Y)
+	assert.True(t, states[0].IsVisible)
+	assert.Equal(t, firstHeight, states[1].Y)
+	assert.False(t, states[1].IsVisible)
+}
+
+func TestAlertStatesReturnsEmptyWithoutAlerts(t *testing.T) {
+	states := New(testTheme()).AlertStates(80, 24)
+
+	assert.Empty(t, states)
+}
+
+func TestAlertColorsByType(t *testing.T) {
+	th := testTheme()
+	model := New(th)
+	tests := []struct {
+		name          string
+		alertType     AlertType
+		wantBorder    color.Color
+		wantIconColor color.Color
+	}{
+		{name: "error", alertType: MsgTypeError, wantBorder: th.Colors.Error, wantIconColor: th.Colors.Error},
+		{name: "warning", alertType: AlertTypeWarning, wantBorder: th.Colors.Warning, wantIconColor: th.Colors.Warning},
+		{name: "info", alertType: AlertTypeInfo, wantBorder: th.Colors.Info, wantIconColor: th.Colors.Info},
+		{name: "default", alertType: AlertType("custom"), wantBorder: th.Colors.Border, wantIconColor: th.Colors.Foreground},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			border, iconColor := model.getColors(Alert{Type: tt.alertType})
+
+			assert.Equal(t, tt.wantBorder, border)
+			assert.Equal(t, tt.wantIconColor, iconColor)
+		})
+	}
+}
+
+func TestUpdateThemeChangesAlertColors(t *testing.T) {
+	originalTheme := testTheme()
+	model := New(originalTheme)
+	updatedTheme := testTheme()
+	updatedTheme.Colors.Info = lipgloss.Color("#00ffff")
+	updatedTheme.Colors.Border = lipgloss.Color("#123456")
+	updatedTheme.Colors.Foreground = lipgloss.Color("#654321")
+	require.NotEqual(t, originalTheme.Colors.Info, updatedTheme.Colors.Info)
+
+	_, originalIconColor := model.getColors(Alert{Type: AlertTypeInfo})
+	require.Equal(t, originalTheme.Colors.Info, originalIconColor)
+
+	model.UpdateTheme(updatedTheme)
+
+	border, iconColor := model.getColors(Alert{Type: AlertTypeInfo})
+	assert.Equal(t, updatedTheme.Colors.Info, border)
+	assert.Equal(t, updatedTheme.Colors.Info, iconColor)
+
+	border, iconColor = model.getColors(Alert{Type: AlertType("custom")})
+	assert.Equal(t, updatedTheme.Colors.Border, border)
+	assert.Equal(t, updatedTheme.Colors.Foreground, iconColor)
+}
+
+func TestRenderAlertContent(t *testing.T) {
+	model := New(testTheme())
+	tests := []struct {
+		name         string
+		alert        Alert
+		wantContains []string
+		wantMissing  []string
+	}{
+		{
+			name:         "title and message",
+			alert:        Alert{Type: AlertTypeInfo, Title: "Saved", Message: "Repository updated"},
+			wantContains: []string{"ℹ Saved", "Repository updated"},
+		},
+		{
+			name:         "title only",
+			alert:        Alert{Type: AlertTypeWarning, Title: "Warning"},
+			wantContains: []string{"⚠ Warning"},
+		},
+		{
+			name:         "message only",
+			alert:        Alert{Type: MsgTypeError, Message: "Push failed"},
+			wantContains: []string{"Push failed"},
+			wantMissing:  []string{"✗"},
+		},
+		{
+			name:         "default type",
+			alert:        Alert{Type: AlertType("custom"), Title: "Notice"},
+			wantContains: []string{"• Notice"},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			view := model.renderAlert(tt.alert)
+
+			for _, want := range tt.wantContains {
+				assert.Contains(t, view, want)
+			}
+			for _, unwanted := range tt.wantMissing {
+				assert.NotContains(t, view, unwanted)
+			}
+		})
+	}
+}
+
+func TestStartTimerReturnsTickMessage(t *testing.T) {
+	cmd := startTimer(0 * time.Millisecond)
+	require.NotNil(t, cmd)
+
+	assert.IsType(t, TickMsg{}, cmd())
+}