pkg/cli/frame.go

@@ -70,6 +70,15 @@ func NewFrame(variant string) *Frame {
 	}
 }
 
+// WithOutput sets the destination writer for rendered output.
+// Pass nil to keep the current writer unchanged.
+func (f *Frame) WithOutput(out io.Writer) *Frame {
+	if out != nil {
+		f.out = out
+	}
+	return f
+}
+
 // Header sets the Header region model.
 func (f *Frame) Header(m Model) *Frame { f.setModel(RegionHeader, m); return f }
 

pkg/cli/frame_test.go

@@ -142,6 +142,16 @@ func TestFrame_Good(t *testing.T) {
 		f := NewFrame("C")
 		assert.Same(t, os.Stderr, f.out)
 	})
+
+	t.Run("WithOutput sets output writer", func(t *testing.T) {
+		var buf bytes.Buffer
+		f := NewFrame("C").WithOutput(&buf)
+		f.Content(StaticModel("timed"))
+
+		f.Run()
+
+		assert.Contains(t, buf.String(), "timed")
+	})
 }
 
 func TestFrame_Bad(t *testing.T) {

pkg/cli/tracker.go

@@ -123,6 +123,15 @@ func NewTaskTracker() *TaskTracker {
 	return &TaskTracker{out: os.Stderr}
 }
 
+// WithOutput sets the destination writer for tracker output.
+// Pass nil to keep the current writer unchanged.
+func (tr *TaskTracker) WithOutput(out io.Writer) *TaskTracker {
+	if out != nil {
+		tr.out = out
+	}
+	return tr
+}
+
 // Add registers a task and returns it for goroutine use.
 func (tr *TaskTracker) Add(name string) *TrackedTask {
 	t := &TrackedTask{

pkg/cli/tracker_test.go

@@ -121,8 +121,7 @@ func TestTaskTracker_Good(t *testing.T) {
 
 	t.Run("wait completes for non-TTY", func(t *testing.T) {
 		var buf bytes.Buffer
-		tr := NewTaskTracker()
-		tr.out = &buf
+		tr := NewTaskTracker().WithOutput(&buf)
 
 		task := tr.Add("quick")
 		go func() {
@@ -135,6 +134,17 @@ func TestTaskTracker_Good(t *testing.T) {
 		assert.Contains(t, buf.String(), "done")
 	})
 
+	t.Run("WithOutput sets output writer", func(t *testing.T) {
+		var buf bytes.Buffer
+		tr := NewTaskTracker().WithOutput(&buf)
+
+		tr.Add("quick").Done("done")
+		tr.Wait()
+
+		assert.Contains(t, buf.String(), "quick")
+		assert.Contains(t, buf.String(), "done")
+	})
+
 	t.Run("name width alignment", func(t *testing.T) {
 		tr := NewTaskTracker()
 		tr.out = &bytes.Buffer{}