From 4bce62e1fa80fe9921c8cc538889286c4df3b028 Mon Sep 17 00:00:00 2001
From: codex-bot-andresmgsl
 <codex-bot-andresmgsl@noreply.forgejo.heavyduty.builders>
Date: Mon, 31 Aug 2026 21:20:35 +0000
Subject: [PATCH] test(labels): prove merge-base fallback

---
 test/labels-reconcile.test.sh | 30 ++++++++++++++++++++++--------
 1 file changed, 22 insertions(+), 8 deletions(-)

diff --git a/test/labels-reconcile.test.sh b/test/labels-reconcile.test.sh
index 9dd71c3..14b7ebc 100755
--- a/test/labels-reconcile.test.sh
+++ b/test/labels-reconcile.test.sh
@@ -176,10 +176,12 @@ expect "a bare head over an unreadable base still warns" yes \
   "$(release_shape_warning 41 2.0.0 "" | grep -qF '::warning::' && echo yes || echo no)"
 
 # The pure matrix above proves the warning predicate. These two fixtures drive
-# the sweep boundary that chooses WHICH base tree feeds it (#275): Forgejo and
-# GitHub both expose the PR's moving base tip beside its fixed merge base, and
-# using the former manufactures a downgrade after an intervening release.
-release_shape_ref_probe() { # $1 = phantom | bump
+# the sweep boundary that chooses WHICH base tree feeds it (#275): the
+# reporting Forgejo payload exposes the PR's moving base tip beside its fixed
+# merge base, and using the former manufactures a downgrade after an
+# intervening release. A missing merge-base field deliberately keeps the
+# specified base-tip fallback for backends that do not supply that fact.
+release_shape_ref_probe() { # $1 = phantom | bump | fallback
   (
     # shellcheck disable=SC2030 # this probe intentionally isolates its repository fixture
     REPO=owner/repo
@@ -190,9 +192,14 @@ release_shape_ref_probe() { # $1 = phantom | bump
     : >"$refs"
     case "$mode" in
       phantom)
-        head_ver=1.3.0 base_tip_ver=1.4.0 merge_base_ver=1.3.0 ;;
+        head_ver=1.3.0 base_tip_ver=1.4.0 merge_base_ver=1.3.0
+        merge_base_json='"merge-base"' ;;
       bump)
-        head_ver=1.4.0 base_tip_ver=1.3.0 merge_base_ver=1.3.0 ;;
+        head_ver=1.4.0 base_tip_ver=1.3.0 merge_base_ver=1.3.0
+        merge_base_json='"merge-base"' ;;
+      fallback)
+        head_ver=1.4.0 base_tip_ver=1.4.0 merge_base_ver=unused
+        merge_base_json=null ;;
       *) return 2 ;;
     esac
     # shellcheck disable=SC2317 # reached through the GitHub backend selected above
@@ -214,8 +221,9 @@ release_shape_ref_probe() { # $1 = phantom | bump
         *'repos/owner/repo/pulls/701 --jq .requested_reviewers'*) return 0 ;;
         *repos/owner/repo/pulls/701/reviews*) return 0 ;;
         *repos/owner/repo/pulls/701)
-          jq -n '{draft:false,user:{login:"fixture-builder"},
-                  head:{sha:"head"},base:{sha:"base-tip"},merge_base:"merge-base",
+          jq -n --argjson merge_base "$merge_base_json" \
+            '{draft:false,user:{login:"fixture-builder"},
+                  head:{sha:"head"},base:{sha:"base-tip"},merge_base:$merge_base,
                   labels:[{name:"state:addressing"},{name:"blocked"}],
                   requested_reviewers:[],created_at:"2026-08-31T20:00:00Z"}' ;;
         *repos/owner/repo/commits/head*) printf '2026-08-31T20:00:00Z\n' ;;
@@ -248,6 +256,12 @@ expect "a genuine version bump relative to the merge base keeps the warning text
 expect "the genuine-bump guard also compares head with the PR merge base" \
   $'head\nmerge-base' "$(cat "$RTMP/release-shape-bump-refs")"
 
+fallback_shape="$(release_shape_ref_probe fallback)"
+expect "a null merge base falls back to the base tip without guessing a warning" \
+  no "$(grep -q 'release-shaped' <<<"$fallback_shape" && echo yes || echo no)"
+expect "the null merge-base fallback compares head with the base tip" \
+  $'head\nbase-tip' "$(cat "$RTMP/release-shape-fallback-refs")"
+
 # -- drafts are building, whoever is requested --------------------------------
 DRAFT=true HEAD_SHA=head1 REQUESTED="" REVIEWS_JSON='[]'
 expect "draft PR is building" state:building "$(decide_state)"