Shallow renderer: support multiple setState invocation (#11167)

Author: Hypnosphi

src/renderers/testing/ReactShallowRendererEntry.js

@@ -205,12 +205,14 @@ class Updater {
   }
 
   enqueueSetState(publicInstance, partialState, callback, callerName) {
+    const currentState = this._renderer._newState || publicInstance.state;
+
     if (typeof partialState === 'function') {
-      partialState = partialState(publicInstance.state, publicInstance.props);
+      partialState = partialState(currentState, publicInstance.props);
     }
 
     this._renderer._newState = {
-      ...publicInstance.state,
+      ...currentState,
       ...partialState,
     };
 

src/renderers/testing/__tests__/ReactShallowRenderer-test.js

@@ -450,6 +450,52 @@ describe('ReactShallowRenderer', () => {
     expect(result).toEqual(<div>doovy</div>);
   });
 
+  it('can setState in componentWillMount repeatedly when shallow rendering', () => {
+    class SimpleComponent extends React.Component {
+      state = {
+        separator: '-',
+      };
+
+      componentWillMount() {
+        this.setState({groovy: 'doovy'});
+        this.setState({doovy: 'groovy'});
+      }
+
+      render() {
+        const {groovy, doovy, separator} = this.state;
+
+        return <div>{`${groovy}${separator}${doovy}`}</div>;
+      }
+    }
+
+    const shallowRenderer = createRenderer();
+    const result = shallowRenderer.render(<SimpleComponent />);
+    expect(result).toEqual(<div>doovy-groovy</div>);
+  });
+
+  it('can setState in componentWillMount with an updater function repeatedly when shallow rendering', () => {
+    class SimpleComponent extends React.Component {
+      state = {
+        separator: '-',
+      };
+
+      componentWillMount() {
+        this.setState(state => ({groovy: 'doovy'}));
+        this.setState(state => ({doovy: state.groovy}));
+      }
+
+      render() {
+        const {groovy, doovy, separator} = this.state;
+
+        return <div>{`${groovy}${separator}${doovy}`}</div>;
+      }
+    }
+
+    const shallowRenderer = createRenderer();
+    const result = shallowRenderer.render(<SimpleComponent />);
+    expect(result).toEqual(<div>doovy-doovy</div>);
+  });
+
   it('can setState in componentWillReceiveProps when shallow rendering', () => {
     class SimpleComponent extends React.Component {
       state = {count: 0};