diff --git a/testing/web-platform/tests/streams/readable-streams/tee.any.js b/testing/web-platform/tests/streams/readable-streams/tee.any.js
index e5d5a48558a4e..a351c6a31b4bd 100644
--- a/testing/web-platform/tests/streams/readable-streams/tee.any.js
+++ b/testing/web-platform/tests/streams/readable-streams/tee.any.js
@@ -2178,6 +2178,306 @@ branches
 '
 )
 ;
+promise_test
+(
+async
+t
+=
+>
+{
+let
+controller
+;
+const
+rs
+=
+new
+ReadableStream
+(
+{
+start
+(
+c
+)
+{
+controller
+=
+c
+;
+}
+}
+)
+;
+const
+[
+reader1
+reader2
+]
+=
+rs
+.
+tee
+(
+)
+.
+map
+(
+branch
+=
+>
+branch
+.
+getReader
+(
+)
+)
+;
+const
+cancelPromise
+=
+reader2
+.
+cancel
+(
+)
+;
+controller
+.
+enqueue
+(
+'
+a
+'
+)
+;
+const
+read1
+=
+await
+reader1
+.
+read
+(
+)
+;
+assert_object_equals
+(
+read1
+{
+value
+:
+'
+a
+'
+done
+:
+false
+}
+'
+first
+read
+(
+)
+from
+branch1
+should
+fulfill
+with
+the
+chunk
+'
+)
+;
+controller
+.
+close
+(
+)
+;
+const
+read2
+=
+await
+reader1
+.
+read
+(
+)
+;
+assert_object_equals
+(
+read2
+{
+value
+:
+undefined
+done
+:
+true
+}
+'
+second
+read
+(
+)
+from
+branch1
+should
+be
+done
+'
+)
+;
+await
+Promise
+.
+all
+(
+[
+reader1
+.
+closed
+cancelPromise
+]
+)
+;
+}
+'
+ReadableStream
+teeing
+:
+canceling
+branch1
+should
+finish
+when
+branch2
+reads
+until
+end
+of
+stream
+'
+)
+;
+promise_test
+(
+async
+t
+=
+>
+{
+let
+controller
+;
+const
+theError
+=
+{
+name
+:
+'
+boo
+!
+'
+}
+;
+const
+rs
+=
+new
+ReadableStream
+(
+{
+start
+(
+c
+)
+{
+controller
+=
+c
+;
+}
+}
+)
+;
+const
+[
+reader1
+reader2
+]
+=
+rs
+.
+tee
+(
+)
+.
+map
+(
+branch
+=
+>
+branch
+.
+getReader
+(
+)
+)
+;
+const
+cancelPromise
+=
+reader2
+.
+cancel
+(
+)
+;
+controller
+.
+error
+(
+theError
+)
+;
+await
+Promise
+.
+all
+(
+[
+promise_rejects_exactly
+(
+t
+theError
+reader1
+.
+read
+(
+)
+)
+cancelPromise
+]
+)
+;
+}
+'
+ReadableStream
+teeing
+:
+canceling
+branch1
+should
+finish
+when
+original
+stream
+errors
+'
+)
+;
 test
 (
 t