update & fix

aircox/test.py

@@ -86,7 +86,7 @@ class WrapperMixin:
         ns_target = getattr(ns, ns_attr, None)
         if self.target is ns_target:
             return
-        elif self.target is not None:
+        elif self.target is not None and self.ns:
             raise RuntimeError(
                 "self target already injected. It must be "
                 "`release` before `inject`."
@@ -97,12 +97,14 @@ class WrapperMixin:
 
         self.ns = ns
         self.ns_attr = ns_attr
+        return self
 
     def release(self):
         """Remove injection from previously injected parent, reset target."""
         if self.ns_target is self.interface:
             setattr(self.ns, self.ns_attr, self.target)
         self.target = None
+        return self
 
 
 class SpoofMixin:
@@ -190,6 +192,16 @@ class Interface:
             self.interface = interface
             super().__init__(**kwargs)
 
+        def clone(self, **kwargs):
+            """Return an Interface copying some values from self."""
+            kwargs.update(
+                {
+                    "target": self.target,
+                    "funcs": self.funcs,
+                }
+            )
+            return type(self.interface)(_imeta_kw=kwargs)._imeta
+
         def __getitem__(self, name):
             return self.traces[name]