1 files changed, 40 insertions, 0 deletions
diff --git a/internal/models/recurrence_test.go b/internal/models/recurrence_test.go
index 8d18996..affba56 100644
--- a/internal/models/recurrence_test.go
+++ b/internal/models/recurrence_test.go
@@ -49,3 +49,43 @@ func TestComputeNextOccurrence(t *testing.T) {
 		})
 	}
 }
+
+func TestCollapseRecurringSeries_KeepsOnlyEarliestOpenInstance(t *testing.T) {
+	sep1 := time.Date(2026, 9, 1, 0, 0, 0, 0, time.UTC)
+	oct1 := time.Date(2026, 10, 1, 0, 0, 0, 0, time.UTC)
+
+	tasks := []Task{
+		{ID: "bills-sep", Content: "Bills", DueDate: &sep1, RecurrenceSeriesID: "bills"},
+		{ID: "bills-oct", Content: "Bills", DueDate: &oct1, RecurrenceSeriesID: "bills"},
+		{ID: "one-off", Content: "Fix curtain holder"},
+	}
+
+	got := CollapseRecurringSeries(tasks)
+
+	var ids []string
+	for _, task := range got {
+		ids = append(ids, task.ID)
+	}
+	if len(got) != 2 {
+		t.Fatalf("got %d tasks (%v), want 2: one row per recurring series plus the one-off", len(got), ids)
+	}
+	if got[0].ID != "bills-sep" {
+		t.Errorf("kept %q for the Bills series, want bills-sep (the earliest open instance is the one you actually owe)", got[0].ID)
+	}
+	if got[1].ID != "one-off" {
+		t.Errorf("non-recurring task was dropped or reordered: got %q", got[1].ID)
+	}
+}
+
+func TestCollapseRecurringSeries_UndatedAndDistinctSeriesUntouched(t *testing.T) {
+	due := time.Date(2026, 9, 1, 0, 0, 0, 0, time.UTC)
+	tasks := []Task{
+		{ID: "a", RecurrenceSeriesID: "series-a", DueDate: &due},
+		{ID: "b", RecurrenceSeriesID: "series-b", DueDate: &due},
+		{ID: "c", RecurrenceSeriesID: "series-c"}, // recurring but undated
+	}
+
+	if got := CollapseRecurringSeries(tasks); len(got) != 3 {
+		t.Errorf("len = %d, want 3 -- distinct series must not collapse into each other", len(got))
+	}
+}