reset bp method for test-scoped app fixtures

src/flask/blueprints.py

@@ -469,6 +469,13 @@ class Blueprint(Scaffold):
             bp_options["name_prefix"] = name
             blueprint.register(app, bp_options)
 
+    def reset_blueprint(self):
+        """Resets this blueprint. Clears registered child blueprints and
+        set _got_registered_once flag to False
+        """
+        self._blueprints = []
+        self._got_registered_once = False
+
     @setupmethod
     def add_url_rule(
         self,

tests/test_nested_blueprints.py

@@ -0,0 +1,30 @@
+import pytest
+
+from flask import Blueprint
+from flask import Flask
+
+parent = Blueprint("parent", __name__)
+child = Blueprint("child", __name__)
+
+
+def create_app():
+    app = Flask(__name__)
+    parent.register_blueprint(child, url_prefix="/child")
+    app.register_blueprint(parent, url_prefix="/parent")
+
+    return app
+
+
+@pytest.fixture
+def app():
+    app = create_app()
+    yield app
+    parent.reset_blueprint()
+
+
+def test_1(app):
+    pass
+
+
+def test_2(app):
+    pass