This test works:
```js
let interaction;

const onRender = jest.fn();

SchedulerTracing.unstable_trace("initial_event", performance.now(), () => {
  const interactions = SchedulerTracing.unstable_getCurrent();
  expect(interactions.size).toBe(1);
  interaction = Array.from(interactions)[0];

  ReactDOM.render(
    <React.Profiler id="profiler" onRender={onRender}>
      <Text text="Hi" />
    </React.Profiler>,
    document.createElement("div")
  );
});

expect(interaction).toBeDefined();
expect(onRender).toHaveBeenCalledTimes(1);
expect(onRender.mock.calls[0][6]).toContain(interaction);
```

But if you wrap it in `act`, it fails:
```js
let interaction;

const onRender = jest.fn();

TestUtils.act(() => {
  SchedulerTracing.unstable_trace("initial_event", performance.now(), () => {
    const interactions = SchedulerTracing.unstable_getCurrent();
    expect(interactions.size).toBe(1);
    interaction = Array.from(interactions)[0];

    ReactDOM.render(
      <React.Profiler id="profiler" onRender={onRender}>
        <Text text="Hi" />
      </React.Profiler>,
      document.createElement("div")
    );
  });

  expect(interaction).toBeDefined();
  expect(onRender).toHaveBeenCalledTimes(1);
  expect(onRender.mock.calls[0][6]).toContain(interaction);
});
```

In the latter case, inside of `ReactFiberScheduler`, the interactions `Set` is empty.
https://github.com/facebook/react/blob/2e5d1a8b9e2c29418a27b24306e4c8d5f8681f4f/packages/react-reconciler/src/ReactFiberScheduler.js#L2119-L2126

Note that this does not seem to impact _updates_, only the initial _mount_. I suspect we just need to wrap a callback or something minor.

I came across this while trying to write profiling tests for the new DevTools. (https://github.com/bvaughn/react-devtools-experimental/pull/258)
let i;
      for (i = 0; i < desiredWillUpdates; i++) {
        expect(willUpdates).toContain(desiredWillUpdates[i]);
      }
      for (i = 0; i < desiredDidUpdates; i++) {
        expect(didUpdates).toContain(desiredDidUpdates[i]);
      }
      willUpdates = [];
      didUpdates = [];
    }
    function triggerUpdate(c) {
      c.setState({x: 1});
    }
    function testUpdates(components, desiredWillUpdates, desiredDidUpdates) {
      let i;
      ReactDOM.unstable_batchedUpdates(function() {
        for (i = 0; i < components.length; i++) {
          triggerUpdate(components[i]);
        }
      });
      expectUpdates(desiredWillUpdates, desiredDidUpdates);
      
      ReactDOM.unstable_batchedUpdates(function() {
        for (i = components.length - 1; i >= 0; i--) {
          triggerUpdate(components[i]);
        }
      });