diff --git a/src/_pytest/config/__init__.py b/src/_pytest/config/__init__.py
index 6c1d9c69a..74168efd5 100644
--- a/src/_pytest/config/__init__.py
+++ b/src/_pytest/config/__init__.py
@@ -256,6 +256,7 @@ default_plugins = essential_plugins + (
 
 builtin_plugins = set(default_plugins)
 builtin_plugins.add("pytester")
+builtin_plugins.add("pytester_assertions")
 
 
 def get_config(
diff --git a/src/_pytest/pytester.py b/src/_pytest/pytester.py
index 0e1dffb9d..158b71b3a 100644
--- a/src/_pytest/pytester.py
+++ b/src/_pytest/pytester.py
@@ -1,4 +1,7 @@
-"""(Disabled by default) support for testing pytest and pytest plugins."""
+"""(Disabled by default) support for testing pytest and pytest plugins.
+
+PYTEST_DONT_REWRITE
+"""
 import collections.abc
 import contextlib
 import gc
@@ -66,6 +69,9 @@ if TYPE_CHECKING:
     import pexpect
 
 
+pytest_plugins = ["pytester_assertions"]
+
+
 IGNORE_PAM = [  # filenames added when obtaining details about the current user
     "/var/lib/sss/mc/passwd"
 ]
@@ -408,16 +414,12 @@ class HookRecorder:
 
     def assertoutcome(self, passed: int = 0, skipped: int = 0, failed: int = 0) -> None:
         __tracebackhide__ = True
+        from _pytest.pytester_assertions import assertoutcome
 
         outcomes = self.listoutcomes()
-        realpassed, realskipped, realfailed = outcomes
-        obtained = {
-            "passed": len(realpassed),
-            "skipped": len(realskipped),
-            "failed": len(realfailed),
-        }
-        expected = {"passed": passed, "skipped": skipped, "failed": failed}
-        assert obtained == expected, outcomes
+        assertoutcome(
+            outcomes, passed=passed, skipped=skipped, failed=failed,
+        )
 
     def clear(self) -> None:
         self.calls[:] = []
@@ -574,25 +576,18 @@ class RunResult:
         """Assert that the specified outcomes appear with the respective
         numbers (0 means it didn't occur) in the text output from a test run."""
         __tracebackhide__ = True
+        from _pytest.pytester_assertions import assert_outcomes
 
-        d = self.parseoutcomes()
-        obtained = {
-            "passed": d.get("passed", 0),
-            "skipped": d.get("skipped", 0),
-            "failed": d.get("failed", 0),
-            "errors": d.get("errors", 0),
-            "xpassed": d.get("xpassed", 0),
-            "xfailed": d.get("xfailed", 0),
-        }
-        expected = {
-            "passed": passed,
-            "skipped": skipped,
-            "failed": failed,
-            "errors": errors,
-            "xpassed": xpassed,
-            "xfailed": xfailed,
-        }
-        assert obtained == expected
+        outcomes = self.parseoutcomes()
+        assert_outcomes(
+            outcomes,
+            passed=passed,
+            skipped=skipped,
+            failed=failed,
+            errors=errors,
+            xpassed=xpassed,
+            xfailed=xfailed,
+        )
 
 
 class CwdSnapshot:
diff --git a/src/_pytest/pytester_assertions.py b/src/_pytest/pytester_assertions.py
new file mode 100644
index 000000000..630c1d333
--- /dev/null
+++ b/src/_pytest/pytester_assertions.py
@@ -0,0 +1,66 @@
+"""Helper plugin for pytester; should not be loaded on its own."""
+# This plugin contains assertions used by pytester. pytester cannot
+# contain them itself, since it is imported by the `pytest` module,
+# hence cannot be subject to assertion rewriting, which requires a
+# module to not be already imported.
+from typing import Dict
+from typing import Sequence
+from typing import Tuple
+from typing import Union
+
+from _pytest.reports import CollectReport
+from _pytest.reports import TestReport
+
+
+def assertoutcome(
+    outcomes: Tuple[
+        Sequence[TestReport],
+        Sequence[Union[CollectReport, TestReport]],
+        Sequence[Union[CollectReport, TestReport]],
+    ],
+    passed: int = 0,
+    skipped: int = 0,
+    failed: int = 0,
+) -> None:
+    __tracebackhide__ = True
+
+    realpassed, realskipped, realfailed = outcomes
+    obtained = {
+        "passed": len(realpassed),
+        "skipped": len(realskipped),
+        "failed": len(realfailed),
+    }
+    expected = {"passed": passed, "skipped": skipped, "failed": failed}
+    assert obtained == expected, outcomes
+
+
+def assert_outcomes(
+    outcomes: Dict[str, int],
+    passed: int = 0,
+    skipped: int = 0,
+    failed: int = 0,
+    errors: int = 0,
+    xpassed: int = 0,
+    xfailed: int = 0,
+) -> None:
+    """Assert that the specified outcomes appear with the respective
+    numbers (0 means it didn't occur) in the text output from a test run."""
+    __tracebackhide__ = True
+
+    obtained = {
+        "passed": outcomes.get("passed", 0),
+        "skipped": outcomes.get("skipped", 0),
+        "failed": outcomes.get("failed", 0),
+        "errors": outcomes.get("errors", 0),
+        "xpassed": outcomes.get("xpassed", 0),
+        "xfailed": outcomes.get("xfailed", 0),
+    }
+    expected = {
+        "passed": passed,
+        "skipped": skipped,
+        "failed": failed,
+        "errors": errors,
+        "xpassed": xpassed,
+        "xfailed": xfailed,
+    }
+    assert obtained == expected