--- a/mercurial/testing/revlog.py	Fri Nov 29 22:55:30 2024 +0100
+++ b/mercurial/testing/revlog.py	Sat Nov 30 19:12:02 2024 +0100
@@ -23,7 +23,10 @@
     b'\x00\x00\x00\x00\x00\x00\x00\x00\x00'
 )
 
-from ..revlogutils.constants import REVLOGV1
+from ..revlogutils.constants import (
+    KIND_CHANGELOG,
+)
+from .. import revlog
 
 
 try:
@@ -32,11 +35,13 @@
     cparsers = None
 
 try:
-    from ..rustext.revlog import (  # pytype: disable=import-error
-        Index as RustIndex,
+    from ..rustext import (  # pytype: disable=import-error
+        revlog as rust_revlog,
     )
+
+    rust_revlog.__name__  # force actual import
 except ImportError:
-    RustIndex = None
+    rust_revlog = None
 
 
 @unittest.skipIf(
@@ -51,14 +56,38 @@
 
 
 @unittest.skipIf(
-    RustIndex is None,
-    'The Rust index is not available. It is needed for this test.',
+    rust_revlog is None,
+    'The Rust revlog module is not available. It is needed for this test.',
 )
 class RustRevlogBasedTestBase(unittest.TestCase):
-    def parserustindex(self, data=None):
+    # defaults
+    revlog_data_config = revlog.DataConfig()
+    revlog_delta_config = revlog.DeltaConfig()
+    revlog_feature_config = revlog.FeatureConfig()
+
+    def make_inner_revlog(
+        self, data=None, vfs_is_readonly=True, kind=KIND_CHANGELOG
+    ):
         if data is None:
             data = data_non_inlined
-        # not inheriting RevlogBasedTestCase to avoid having a
-        # `parseindex` method that would be shadowed by future subclasses
-        # this duplication will soon be removed
-        return RustIndex(data, REVLOGV1)
+
+        return rust_revlog.InnerRevlog(
+            vfs_base=b"Just a path",
+            fncache=None,  # might be enough for now
+            vfs_is_readonly=vfs_is_readonly,
+            index_data=data,
+            index_file=b'test.i',
+            data_file=b'test.d',
+            sidedata_file=None,
+            inline=False,
+            data_config=self.revlog_data_config,
+            delta_config=self.revlog_delta_config,
+            feature_config=self.revlog_feature_config,
+            chunk_cache=None,
+            default_compression_header=None,
+            revlog_type=kind,
+            use_persistent_nodemap=False,  # until we cook one.
+        )
+
+    def parserustindex(self, data=None):
+        return revlog.RustIndexProxy(self.make_inner_revlog(data=data))

--- a/tests/test-rust-ancestor.py	Fri Nov 29 22:55:30 2024 +0100
+++ b/tests/test-rust-ancestor.py	Sat Nov 30 19:12:02 2024 +0100
@@ -1,5 +1,4 @@
 import sys
-import unittest
 
 from mercurial.node import wdirrev
 
@@ -26,16 +25,6 @@
     cparsers = None
 
 
-@unittest.skipIf(
-    rustext is None,
-    'The Rust version of the "ancestor" module is not available. It is needed'
-    ' for this test.',
-)
-@unittest.skipIf(
-    rustext is None,
-    'The Rust or C version of the "parsers" module, which the "ancestor" module'
-    ' relies on, is not available.',
-)
 class rustancestorstest(revlogtesting.RustRevlogBasedTestBase):
     """Test the correctness of binding to Rust code.
 
@@ -64,16 +53,15 @@
 
     def testlazyancestors(self):
         idx = self.parserustindex()
-        start_count = sys.getrefcount(idx)  # should be 2 (see Python doc)
+        start_count = sys.getrefcount(idx.inner)  # should be 2 (see Python doc)
         self.assertEqual(
             {i: (r[5], r[6]) for i, r in enumerate(idx)},
             {0: (-1, -1), 1: (0, -1), 2: (1, -1), 3: (2, -1)},
         )
         lazy = LazyAncestors(idx, [3], 0, True)
-        # we have two more references to the index:
-        # - in its inner iterator for __contains__ and __bool__
-        # - in the LazyAncestors instance itself (to spawn new iterators)
-        self.assertEqual(sys.getrefcount(idx), start_count + 2)
+        # the LazyAncestors instance holds just one reference to the
+        # inner revlog.
+        self.assertEqual(sys.getrefcount(idx.inner), start_count + 1)
 
         self.assertTrue(2 in lazy)
         self.assertTrue(bool(lazy))
@@ -83,11 +71,11 @@
 
         # now let's watch the refcounts closer
         ait = iter(lazy)
-        self.assertEqual(sys.getrefcount(idx), start_count + 3)
+        self.assertEqual(sys.getrefcount(idx.inner), start_count + 2)
         del ait
-        self.assertEqual(sys.getrefcount(idx), start_count + 2)
+        self.assertEqual(sys.getrefcount(idx.inner), start_count + 1)
         del lazy
-        self.assertEqual(sys.getrefcount(idx), start_count)
+        self.assertEqual(sys.getrefcount(idx.inner), start_count)
 
         # let's check bool for an empty one
         self.assertFalse(LazyAncestors(idx, [0], 0, False))
@@ -111,16 +99,16 @@
 
     def testrefcount(self):
         idx = self.parserustindex()
-        start_count = sys.getrefcount(idx)
+        start_count = sys.getrefcount(idx.inner)
 
         # refcount increases upon iterator init...
         ait = AncestorsIterator(idx, [3], 0, True)
-        self.assertEqual(sys.getrefcount(idx), start_count + 1)
+        self.assertEqual(sys.getrefcount(idx.inner), start_count + 1)
         self.assertEqual(next(ait), 3)
 
         # and decreases once the iterator is removed
         del ait
-        self.assertEqual(sys.getrefcount(idx), start_count)
+        self.assertEqual(sys.getrefcount(idx.inner), start_count)
 
         # and removing ref to the index after iterator init is no issue
         ait = AncestorsIterator(idx, [3], 0, True)