Make scry* look through stateless components

Fixes #4882.

src/test/ReactTestUtils.js

@@ -44,6 +44,7 @@ function findAllInRenderedTreeInternal(inst, test) {
   }
   var publicInst = inst.getPublicInstance();
   var ret = test(publicInst) ? [publicInst] : [];
+  var currentElement = inst._currentElement;
   if (ReactTestUtils.isDOMComponent(publicInst)) {
     var renderedChildren = inst._renderedChildren;
     var key;
@@ -58,7 +59,10 @@ function findAllInRenderedTreeInternal(inst, test) {
         )
       );
     }
-  } else if (ReactTestUtils.isCompositeComponent(publicInst)) {
+  } else if (
+    ReactElement.isValidElement(currentElement) &&
+    typeof currentElement.type === 'function'
+  ) {
     ret = ret.concat(
       findAllInRenderedTreeInternal(inst._renderedComponent, test)
     );
@@ -111,7 +115,8 @@ var ReactTestUtils = {
       // this returns when we have DOM nodes as refs directly
       return false;
     }
-    return typeof inst.render === 'function' &&
+    return inst != null &&
+           typeof inst.render === 'function' &&
            typeof inst.setState === 'function';
   },
 

src/test/__tests__/ReactTestUtils-test.js

@@ -410,4 +410,22 @@ describe('ReactTestUtils', function() {
     expect(handler).toHaveBeenCalledWith(jasmine.objectContaining({target: node}));
   });
 
+  it('can scry with stateless components involved', function() {
+    var Stateless = () => <div><hr /></div>;
+    var SomeComponent = React.createClass({
+      render: function() {
+        return (
+          <div>
+            <Stateless />
+            <hr />
+          </div>
+        );
+      },
+    });
+
+    var inst = ReactTestUtils.renderIntoDocument(<SomeComponent />);
+    var hrs = ReactTestUtils.scryRenderedDOMComponentsWithTag(inst, 'hr');
+    expect(hrs.length).toBe(2);
+  });
+
 });