Dont call memo comparison function on initial render

packages/react-test-renderer/src/ReactShallowRenderer.js

@@ -583,7 +583,8 @@ class ReactShallowRenderer {
         let shouldRender = true;
         if (
           isMemo(element.type) &&
-          elementType === this._previousComponentIdentity
+          elementType === this._previousComponentIdentity &&
+          previousElement !== null
         ) {
           // This is a Memo component that is being re-rendered.
           const compare = element.type.compare || shallowEqual;

packages/react-test-renderer/src/__tests__/ReactShallowRenderer-test.js

@@ -1510,6 +1510,17 @@ describe('ReactShallowRenderer', () => {
     expect(renderCount).toBe(2);
   });
 
+  it('should not call the comparison function with React.memo on the initial render', () => {
+    const areEqual = jest.fn(() => false);
+    const SomeComponent = React.memo(({foo}) => {
+      return <div>{foo}</div>;
+    }, areEqual);
+    const shallowRenderer = createRenderer();
+    shallowRenderer.render(<SomeComponent foo={1} />);
+    expect(areEqual).not.toHaveBeenCalled();
+    expect(shallowRenderer.getRenderOutput()).toEqual(<div>1</div>);
+  });
+
   it('should handle memo(forwardRef())', () => {
     const testRef = React.createRef();
     const SomeComponent = React.forwardRef((props, ref) => {
@@ -1548,7 +1559,7 @@ describe('ReactShallowRenderer', () => {
         'Warning: forwardRef requires a render function but received ' +
           'a `memo` component. Instead of forwardRef(memo(...)), use ' +
           'memo(forwardRef(...))',
-          {withoutStack: true}
+        {withoutStack: true},
       );
     }).toThrowError(
       'forwardRef requires a render function but was given object.',