diff --git a/tests/perftest.py b/tests/perftest.py
--- a/tests/perftest.py
+++ b/tests/perftest.py
@@ -7,7 +7,6 @@
 from mercurial import (
     error,
     manifest,
-    mdiff,
     registrar,
     vfs as vfsmod,
 )
@@ -165,9 +164,6 @@
         except KeyError:
             deltabase = nullid
             delta = text
-            if False and m1.node() != nullid:
-                deltabase = m1.node()
-                delta = mdiff.textdiff(m1.dirtext(usemfv2), text)
             pack.add(m._dir, n, deltabase, delta)
         cache.add(m._dir, n, text)
     m.setnode(n)
diff --git a/tests/treemanifest_correctness.py b/tests/treemanifest_correctness.py
--- a/tests/treemanifest_correctness.py
+++ b/tests/treemanifest_correctness.py
@@ -7,7 +7,6 @@
 # GNU General Public License version 2 or any later version.
 from mercurial import (
     manifest,
-    mdiff,
     registrar,
 )
 from mercurial.node import nullid
@@ -160,9 +159,6 @@
         except KeyError:
             deltabase = nullid
             delta = text
-            if False and m1.node() != nullid:
-                deltabase = m1.node()
-                delta = mdiff.textdiff(m1.dirtext(usemfv2), text)
             pack.add(m._dir, n, deltabase, delta)
         cache.add(m._dir, n, text)
     m.setnode(n)