Change: promote POSTMERGETESTS, add some explanation

1 files changed, 8 insertions, 3 deletions

diff --git a/ci-arch.mdwn b/ci-arch.mdwn
index 4e0bd91..1a57945 100644
--- a/ci-arch.mdwn
+++ b/ci-arch.mdwn
@@ -153,6 +153,14 @@ future CI system.
       declare at least parts of the pipeline jobs in the repository:
       what commands to run for building, testing, etc.
 
+* **POSTMERGETESTS** All automated tests must pass both before and
+  after merging a change. This can be achieved by various means (run
+  tests twice, or make sure target branch doesn't change in between).
+  The justification is that the way Gerrit and Zuul currently work,
+  the target branch may change while other changes are reviewed and
+  tested, so we run some test after a merge (but possibly before
+  publishing the merge?). FIXME: is this adequate?
+
 ## Hard requirements
 
 These are not absolute requirements, and can be negotiated, but only
@@ -262,9 +270,6 @@ to a minor degree.
   haven't broken anything. An example would be changes to Debian, upon
   which we base our container images.
 
-* **POSTMERGETESTS** Must support post-merge testing. FIXME: This
-  needs to be explained.
-
 * **CIMERGES** Must support tooling to do the merging, instead of
   developers. We don't want developer merging by hand and pushing the
   merges. CI should test changes and merge only if tests pass, so that