1 files changed, 114 insertions, 0 deletions
diff --git a/internal/store/chains_test.go b/internal/store/chains_test.go
index 6359d11..bcfc09e 100644
--- a/internal/store/chains_test.go
+++ b/internal/store/chains_test.go
@@ -263,3 +263,117 @@ func TestGetChain_UnknownID_ReturnsErrNotFound(t *testing.T) {
 		t.Errorf("err = %v, want ErrNativeTaskNotFound", err)
 	}
 }
+
+// TestDeleteNativeTask_LockedChainTask_ClosesPositionGap proves deleting a
+// not-yet-reached chain step doesn't strand the chain: positions after the
+// deleted one shift down by one and stay a contiguous 0..N-1 sequence, since
+// advanceChain's chain_position+1 lookup depends on that contiguity.
+func TestDeleteNativeTask_LockedChainTask_ClosesPositionGap(t *testing.T) {
+	s := newNativeTasksTestStore(t)
+
+	chain, err := s.CreateChain("Track", chainTasks("Step 1", "Step 2", "Step 3"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	tasks, err := s.GetChainTasks(chain.ID)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if err := s.DeleteNativeTask(tasks[1].ID); err != nil {
+		t.Fatalf("DeleteNativeTask: %v", err)
+	}
+
+	after, err := s.GetChainTasks(chain.ID)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(after) != 2 {
+		t.Fatalf("len(after) = %d, want 2", len(after))
+	}
+	if after[0].Content != "Step 1" || after[1].Content != "Step 3" {
+		t.Errorf("unexpected content order: %q, %q", after[0].Content, after[1].Content)
+	}
+	if after[1].ChainPosition != 1 {
+		t.Errorf("Step 3 chain_position = %d, want 1 (gap closed)", after[1].ChainPosition)
+	}
+	if !after[0].ChainUnlocked {
+		t.Errorf("position 0 should still be unlocked")
+	}
+	if after[1].ChainUnlocked {
+		t.Errorf("position 1 (formerly locked position 2) should still be locked")
+	}
+
+	// Completing position 0 should now correctly advance to the
+	// renumbered position 1 (Step 3), proving advanceChain's
+	// chain_position+1 lookup still works post-deletion.
+	if err := s.CompleteNativeTask(after[0].ID); err != nil {
+		t.Fatalf("CompleteNativeTask: %v", err)
+	}
+	final, err := s.GetChainTasks(chain.ID)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !final[1].ChainUnlocked {
+		t.Errorf("Step 3 should be unlocked after completing Step 1")
+	}
+}
+
+// TestDeleteNativeTask_UnlockedChainTask_PromotesSuccessor proves deleting
+// the currently-actionable (unlocked) step unlocks whatever now sits at its
+// position, rather than leaving the chain with nothing unlocked.
+func TestDeleteNativeTask_UnlockedChainTask_PromotesSuccessor(t *testing.T) {
+	s := newNativeTasksTestStore(t)
+
+	chain, err := s.CreateChain("Track", chainTasks("Step 1", "Step 2"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	tasks, err := s.GetChainTasks(chain.ID)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if err := s.DeleteNativeTask(tasks[0].ID); err != nil {
+		t.Fatalf("DeleteNativeTask: %v", err)
+	}
+
+	after, err := s.GetChainTasks(chain.ID)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(after) != 1 {
+		t.Fatalf("len(after) = %d, want 1", len(after))
+	}
+	if !after[0].ChainUnlocked || after[0].DueDate == nil {
+		t.Errorf("Step 2 should be promoted to unlocked with a due date, got ChainUnlocked=%v DueDate=%v", after[0].ChainUnlocked, after[0].DueDate)
+	}
+}
+
+// TestDeleteNativeTask_LastRemainingChainTask_MarksChainCompleted proves
+// deleting the sole unlocked task with nothing left to promote finishes the
+// chain instead of leaving it active with zero unlocked tasks forever.
+func TestDeleteNativeTask_LastRemainingChainTask_MarksChainCompleted(t *testing.T) {
+	s := newNativeTasksTestStore(t)
+
+	chain, err := s.CreateChain("Track", chainTasks("Only step"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	tasks, err := s.GetChainTasks(chain.ID)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if err := s.DeleteNativeTask(tasks[0].ID); err != nil {
+		t.Fatalf("DeleteNativeTask: %v", err)
+	}
+
+	updatedChain, err := s.GetChain(chain.ID)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if updatedChain.Status != "completed" {
+		t.Errorf("chain.Status = %q, want completed", updatedChain.Status)
+	}
+}