From ff219fd11090d00314bf16a71543e431a22b795c Mon Sep 17 00:00:00 2001
From: Chili Palmer <hugoms@me.com>
Date: Sat, 9 May 2026 16:38:18 +0200
Subject: [PATCH] chore: unit test for csm-014

---
 test/bds/csm014_length_in_loop_test.exs | 101 ++++++++++++++++++++++++
 1 file changed, 101 insertions(+)
 create mode 100644 test/bds/csm014_length_in_loop_test.exs

diff --git a/test/bds/csm014_length_in_loop_test.exs b/test/bds/csm014_length_in_loop_test.exs
new file mode 100644
index 0000000..eccb99c
--- /dev/null
+++ b/test/bds/csm014_length_in_loop_test.exs
@@ -0,0 +1,101 @@
+defmodule BDS.CSM014LengthInLoopTest do
+  use ExUnit.Case, async: true
+
+  alias BDS.Generation.Outputs
+
+  describe "build_paginated_archive_outputs/5 pagination correctness" do
+    test "pagination values are consistent across pages" do
+      posts = Enum.map(1..25, fn i -> %{id: i, slug: "post-#{i}"} end)
+
+      plan = %{
+        language: "en",
+        max_posts_per_page: 10
+      }
+
+      collected = :ets.new(:pagination_collector, [:bag, :public])
+
+      Outputs.build_paginated_archive_outputs(
+        plan,
+        ["en"],
+        ["category", "tech"],
+        posts,
+        fn _page_posts, _language, pagination ->
+          :ets.insert(collected, {:pagination, pagination})
+          ""
+        end
+      )
+
+      paginations =
+        :ets.lookup(collected, :pagination)
+        |> Enum.map(fn {:pagination, p} -> p end)
+        |> Enum.sort_by(& &1.current_page)
+
+      :ets.delete(collected)
+
+      assert length(paginations) == 3
+
+      assert Enum.all?(paginations, fn p -> p.total_items == 25 end)
+      assert Enum.all?(paginations, fn p -> p.total_pages == 3 end)
+
+      [p1, p2, p3] = paginations
+      assert p1.has_prev_page == false
+      assert p1.has_next_page == true
+      assert p2.has_prev_page == true
+      assert p2.has_next_page == true
+      assert p3.has_prev_page == true
+      assert p3.has_next_page == false
+    end
+
+    test "single-page result has correct pagination" do
+      posts = [%{id: 1, slug: "only"}]
+
+      plan = %{language: "en", max_posts_per_page: 10}
+
+      collected = :ets.new(:pagination_single, [:bag, :public])
+
+      Outputs.build_paginated_archive_outputs(
+        plan,
+        ["en"],
+        ["tag", "elixir"],
+        posts,
+        fn _page_posts, _language, pagination ->
+          :ets.insert(collected, {:pagination, pagination})
+          ""
+        end
+      )
+
+      [{:pagination, p}] = :ets.lookup(collected, :pagination)
+      :ets.delete(collected)
+
+      assert p.total_items == 1
+      assert p.total_pages == 1
+      assert p.has_prev_page == false
+      assert p.has_next_page == false
+    end
+  end
+
+  describe "linear time with large lists" do
+    test "build_paginated_archive_outputs completes in linear time with 1000 posts" do
+      posts = Enum.map(1..1000, fn i -> %{id: i, slug: "post-#{i}"} end)
+
+      plan = %{
+        language: "en",
+        max_posts_per_page: 10
+      }
+
+      {time_us, results} =
+        :timer.tc(fn ->
+          Outputs.build_paginated_archive_outputs(
+            plan,
+            ["en"],
+            ["category", "big"],
+            posts,
+            fn _page_posts, _language, _pagination -> "" end
+          )
+        end)
+
+      assert length(results) == 100
+      assert time_us < 1_000_000
+    end
+  end
+end