--- a/tests/test-transaction-rollback-on-revlog-split.t	Tue May 18 02:35:27 2021 +0200
+++ b/tests/test-transaction-rollback-on-revlog-split.t	Wed May 19 13:46:19 2021 +0200
@@ -1,7 +1,27 @@
 Test correctness of revlog inline -> non-inline transition
 ----------------------------------------------------------
 
+Helper extension to intercept renames.
+
+  $ cat > $TESTTMP/intercept_rename.py << EOF
+  > import os
+  > import sys
+  > from mercurial import extensions, util
+  > 
+  > def extsetup(ui):
+  >     def close(orig, *args, **kwargs):
+  >         path = args[0]._atomictempfile__name
+  >         if path.endswith(b'/.hg/store/data/file.i'):
+  >             os._exit(80)
+  >         return orig(*args, **kwargs)
+  >     extensions.wrapfunction(util.atomictempfile, 'close', close)
+  > EOF
+
+
 Test offset computation to correctly factor in the index entries themselve.
+Also test that the new data size has the correct size if the transaction is aborted
+after the index has been replaced.
+
 Test repo has one small, one moderate and one big change. The clone has
 the small and moderate change and will transition to non-inline storage when
 adding the big change.
@@ -18,6 +38,12 @@
 
   $ hg clone -r 1 troffset-computation troffset-computation-copy --config format.revlog-compression=none -q
   $ cd troffset-computation-copy
+
+Reference size:
+
+  $ f -s .hg/store/data/file*
+  .hg/store/data/file.i: size=1174
+
   $ cat > .hg/hgrc <<EOF
   > [hooks]
   > pretxnchangegroup = python:$TESTDIR/helper-killhook.py:killme
@@ -33,3 +59,42 @@
 #endif
   $ cat .hg/store/journal | tr -s '\000' ' ' | grep data/file | tail -1
   data/file.i 128
+
+The first file.i entry should match the size above.
+The first file.d entry is the temporary record during the split,
+the second entry after the split happened. The sum of the second file.d
+and the second file.i entry should match the first file.i entry.
+
+  $ cat .hg/store/journal | tr -s '\000' ' ' | grep data/file
+  data/file.i 1174
+  data/file.d 0
+  data/file.d 1046
+  data/file.i 128
+  $ cd ..
+
+Now retry the same but intercept the rename of the index and check that
+the journal does not contain the new index size. This demonstrates the edge case
+where the data file is left as garbage.
+
+  $ hg clone -r 1 troffset-computation troffset-computation-copy2 --config format.revlog-compression=none -q
+  $ cd troffset-computation-copy2
+  $ cat > .hg/hgrc <<EOF
+  > [extensions]
+  > intercept_rename = $TESTTMP/intercept_rename.py
+  > [hooks]
+  > pretxnchangegroup = python:$TESTDIR/helper-killhook.py:killme
+  > EOF
+#if chg
+  $ hg pull ../troffset-computation
+  pulling from ../troffset-computation
+  [255]
+#else
+  $ hg pull ../troffset-computation
+  pulling from ../troffset-computation
+  [80]
+#endif
+  $ cat .hg/store/journal | tr -s '\000' ' ' | grep data/file
+  data/file.i 1174
+  data/file.d 0
+  data/file.d 1046
+  $ cd ..