Added custom cache option to MockedProvider

Changelog.md

@@ -1,5 +1,10 @@
 # Change log
 
+## 2.1.8 (June 28, 2018)
+
+- Allow a custom `Cache` to be passed into `MockedProvider` via props.  
+  [@2142](https://github.com/JakeDawkins) in [#2142](https://github.com/apollographql/react-apollo/pull/2142)
+
 ## 2.1.7 (June 27, 2018)
 
 - The `ApolloProvider` `children` prop type has been changed from `element`

src/test-utils.tsx

@@ -18,7 +18,7 @@ export class MockedProvider extends React.Component<any, any> {
     const link = new MockLink(this.props.mocks, this.props.addTypename);
     this.client = new ApolloClient({
       link,
-      cache: new Cache({ addTypename: this.props.addTypename }),
+      cache: this.props.cache || new Cache({ addTypename: this.props.addTypename }),
       defaultOptions: this.props.defaultOptions,
     });
   }

test/test-utils.test.tsx

@@ -227,3 +227,32 @@ it('errors if the query in the mock and component do not match', done => {
     </MockedProvider>,
   );
 });
+
+it('allows a custom cache to be used for the MockedProvider', done => {
+  const customCache = new InMemoryCache();
+  customCache.writeQuery({ query, variables, data: { user: { ...user, id: 'custom' } } });
+
+  class Container extends React.Component<ChildProps<Variables, Data, Variables>> {
+    componentWillReceiveProps(nextProps: ChildProps<Variables, Data, Variables>) {
+      expect(nextProps.data!.user!.id).toEqual('custom');
+      done();
+    }
+
+    render() {
+      return null;
+    }
+  }
+
+  const ContainerWithData = graphql<Variables, Data, Variables>(query, {
+    options: props => ({
+      variables: props,
+      fetchPolicy: 'cache-only',
+    }),
+  })(Container);
+
+  renderer.create(
+    <MockedProvider mocks={mocks} cache={customCache} addTypename={false}>
+      <ContainerWithData {...variables} />
+    </MockedProvider>,
+  );
+});