diff --git a/src/click/testing.py b/src/click/testing.py
index 7c0e8741e2..04d263eeac 100644
--- a/src/click/testing.py
+++ b/src/click/testing.py
@@ -99,6 +99,18 @@ def __init__(self) -> None:
         self.stdout: io.BytesIO = BytesIOCopy(copy_to=self.output)
         self.stderr: io.BytesIO = BytesIOCopy(copy_to=self.output)
 
+    def __del__(self) -> None:
+        """
+        Guarantee that embedded file-like objects are closed in a
+        predictable order, protecting against races between
+        self.output being closed and other streams being flushed on close
+
+        .. versionadded:: 8.2.2
+        """
+        self.stderr.close()
+        self.stdout.close()
+        self.output.close()
+
 
 class _NamedTextIOWrapper(io.TextIOWrapper):
     def __init__(
diff --git a/tests/test_testing.py b/tests/test_testing.py
index 0fd6973ae8..11fe29dc5d 100644
--- a/tests/test_testing.py
+++ b/tests/test_testing.py
@@ -448,8 +448,7 @@ def test_isolation_stderr_errors():
 
     with runner.isolation() as (_, err, _):
         click.echo("\udce2", err=True, nl=False)
-
-    assert err.getvalue() == b"\\udce2"
+        assert err.getvalue() == b"\\udce2"
 
 
 def test_isolation_flushes_unflushed_stderr():
@@ -460,8 +459,7 @@ def test_isolation_flushes_unflushed_stderr():
 
     with runner.isolation() as (_, err, _):
         click.echo("\udce2", err=True, nl=False)
-
-    assert err.getvalue() == b"\\udce2"
+        assert err.getvalue() == b"\\udce2"
 
     @click.command()
     def cli():