Configure react-test-renderer as a secondary (#13164)

Author: aweary

src/ReactTestHostConfig.js

@@ -180,7 +180,7 @@ export function createTextInstance(
   };
 }
 
-export const isPrimaryRenderer = true;
+export const isPrimaryRenderer = false;
 // This approach enables `now` to be mocked by tests,
 // Even after the reconciler has initialized and read host config values.
 export const now = () => TestRendererScheduling.nowImplementation();

src/__tests__/ReactTestRenderer-test.internal.js

@@ -16,6 +16,10 @@ const React = require('react');
 const ReactTestRenderer = require('react-test-renderer');
 const prettyFormat = require('pretty-format');
 
+// Isolate noop renderer
+jest.resetModules();
+const ReactNoop = require('react-noop-renderer');
+
 // Kind of hacky, but we nullify all the instances to test the tree structure
 // with jasmine's deep equality function, and test the instances separate. We
 // also delete children props because testing them is more annoying and not
@@ -1000,4 +1004,19 @@ describe('ReactTestRenderer', () => {
       }),
     );
   });
+
+  it('can concurrently render context with a "primary" renderer', () => {
+    const Context = React.createContext(null);
+    const Indirection = React.Fragment;
+    const App = () => (
+      <Context.Provider>
+        <Indirection>
+          <Context.Consumer>{() => null}</Context.Consumer>
+        </Indirection>
+      </Context.Provider>
+    );
+    ReactNoop.render(<App />);
+    ReactNoop.flush();
+    ReactTestRenderer.create(<App />);
+  });
 });