repurpose .update() to handle impure renders and props/state mutation

docs/README.md

@@ -67,6 +67,7 @@
     * [text()](/docs/api/ShallowWrapper/text.md)
     * [type()](/docs/api/ShallowWrapper/type.md)
     * [unmount()](/docs/api/ShallowWrapper/unmount.md)
+    * [update()](/docs/api/ShallowWrapper/update.md)
   * [Full DOM Rendering](/docs/api/mount.md)
     * [at(index)](/docs/api/ReactWrapper/at.md)
     * [contains(nodeOrNodes)](/docs/api/ReactWrapper/contains.md)

docs/api/ShallowWrapper/update.md

@@ -0,0 +1,33 @@
+# `.update() => Self`
+
+Forces a re-render. Useful to run before checking the render output if something external
+may be updating the state of the component somewhere.
+
+NOTE: can only be called on a wrapper instance that is also the root instance.
+
+
+#### Returns
+
+`ShallowWrapper`: Returns itself.
+
+
+
+#### Example
+
+```jsx
+class ImpureRender extends React.Component {
+  constructor(props) {
+    super(props);
+    this.count = 0;
+  }
+  render() {
+    return <div>{this.count++}</div>
+  }
+}
+```
+```jsx
+const wrapper = shallow(<ImpureRender />);
+expect(wrapper.text()).to.equal("0");
+wrapper.update();
+expect(wrapper.text()).to.equal("1");
+```

docs/api/shallow.md

@@ -169,6 +169,9 @@ Manually sets context of the root component.
 #### [`.instance() => ReactComponent`](ShallowWrapper/instance.md)
 Returns the instance of the root component.
 
+#### [`.update() => ShallowWrapper`](ShallowWrapper/update.md)
+Calls `.forceUpdate()` on the root component instance.
+
 #### [`.debug() => String`](ShallowWrapper/debug.md)
 Returns a string representation of the current shallow render tree for debugging purposes.
 

src/ShallowWrapper.js

@@ -145,10 +145,23 @@ class ShallowWrapper {
   }
 
   /**
-   * @deprecated
+   * Forces a re-render. Useful to run before checking the render output if something external
+   * may be updating the state of the component somewhere.
+   *
+   * NOTE: can only be called on a wrapper instance that is also the root instance.
+   *
    * @returns {ShallowWrapper}
    */
   update() {
+    if (this.root !== this) {
+      throw new Error('ShallowWrapper::update() can only be called on the root');
+    }
+    this.single(() => {
+      const instance = this.instance();
+      if (instance) {
+        instance.forceUpdate();
+      }
+    });
     return this;
   }
 

test/ShallowWrapper-spec.jsx

@@ -3726,24 +3726,37 @@ describe('shallow', () => {
     }
 
     class Test extends React.Component {
+      componentWillMount() {
+        this.state = {};
+      }
+
       safeSetState(newState) {
         withSetStateAllowed(() => {
           this.setState(newState);
         });
       }
 
-      asyncUpdate() {
+      asyncSetState() {
         setImmediate(() => {
           this.safeSetState({ showSpan: true });
         });
       }
 
+      mutateState() {
+        this.state.showSpan = true;
+      }
+
+      callbackSetState() {
+        this.safeSetState({ showSpan: true });
+      }
+
       render() {
         return (
           <div>
             {this.state && this.state.showSpan && <span className="show-me" />}
-            <button className="async-btn" onClick={() => this.asyncUpdate()} />
-            <Child callback={() => this.safeSetState({ showSpan: true })} />
+            <button className="async-btn" onClick={() => this.asyncSetState()} />
+            <button className="mutates-btn" onClick={() => this.mutateState()} />
+            <Child callback={() => this.callbackSetState()} />
           </div>
         );
       }
@@ -3763,6 +3776,13 @@ describe('shallow', () => {
       wrapper.find(Child).props().callback();
       expect(wrapper.find('.show-me').length).to.equal(1);
     });
+
+    it('should have updated output after state mutation when .update() is called', () => {
+      const wrapper = shallow(<Test />);
+      wrapper.find('.mutates-btn').simulate('click');
+      wrapper.update();
+      expect(wrapper.find('.show-me').length).to.equal(1);
+    });
   });
 
   describe('#single()', () => {