--- a/Lib/importlib/test/util.py
+++ b/Lib/importlib/test/util.py
@@ -24,6 +24,34 @@
                             "requires a case-insensitive filesystem")(test)
 
 
+def set_bootstrap(importlib, bootstrap):
+    """Set importlib to use the passed bootstrap module."""
+    importlib._w_long = bootstrap._w_long
+    importlib._r_long = bootstrap._r_long
+    importlib._bootstrap = bootstrap
+    importlib.__import__ = bootstrap.__import__
+    sys.modules['importlib._bootstrap'] = bootstrap
+
+
+@contextmanager
+def bootstrap_context(importlib, bootstrap):
+    """Temporarily use an alternate bootstrap module."""
+    old_bootstrap = importlib._bootstrap
+    try:
+        set_bootstrap(importlib, bootstrap)
+        yield
+    finally:
+        set_bootstrap(importlib, old_bootstrap)
+
+
+def pure_bootstrap_context(importlib):
+    """Temporarily use importlib._bootstrap."""
+    # importlib._bootstrap will normally be the same as _frozen_importlib
+    if not hasattr(importlib._pure_bootstrap, 'sys'):
+        importlib._pure_bootstrap._setup(sys, imp)
+    return bootstrap_context(importlib, importlib._pure_bootstrap)
+
+
 @contextmanager
 def uncache(*names):
     """Uncache a module from sys.modules.