Fix test renderer unmount

scripts/fiber/tests-passing.txt

@@ -1552,6 +1552,7 @@ src/renderers/testing/__tests__/ReactTestRenderer-test.js
 * warns correctly for refs on SFCs
 * allows an optional createNodeMock function
 * supports unmounting when using refs
+* supports unmounting inner instances
 * supports updates when using refs
 * supports error boundaries
 

src/renderers/testing/ReactTestRenderer.js

@@ -121,7 +121,10 @@ class ReactTestComponent {
   }
 
   getHostNode(): void {}
-  unmountComponent(): void {}
+  unmountComponent(safely, skipLifecycle): void {
+    // $FlowFixMe https://github.com/facebook/flow/issues/1805
+    this.unmountChildren(safely, skipLifecycle);
+  }
 }
 
 Object.assign(ReactTestComponent.prototype, ReactMultiChild);

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

@@ -326,6 +326,24 @@ describe('ReactTestRenderer', () => {
     expect(() => inst.unmount()).not.toThrow();
   });
 
+  it('supports unmounting inner instances', () => {
+    let count = 0;
+    class Foo extends React.Component {
+      componentWillUnmount() {
+        count++;
+      }
+      render() {
+        return <div />;
+      }
+    }
+    const inst = ReactTestRenderer.create(
+      <div><Foo /></div>,
+      {createNodeMock: () => 'foo'}
+    );
+    expect(() => inst.unmount()).not.toThrow();
+    expect(count).toEqual(1);
+  });
+
   it('supports updates when using refs', () => {
     const log = [];
     const createNodeMock = element => {