test: fix React.createContext mock

tests/__mocks__/react.js

@@ -1,11 +1,9 @@
+import createReactContext from 'create-react-context/lib/implementation';
+
 const React = require.requireActual('react');
 
 if (!React.createContext) {
-  React.createContext = () => {
-    const Provider = ({ children }) => children;
-    const Consumer = ({ children }) => children();
-    return { Provider, Consumer };
-  };
+  React.createContext = createReactContext;
 }
 
 if (!React.createRef) {