Warn when rendering tests in concurrent/batched mode without a mocked scheduler (#16207)

Concurrent/Batched mode tests should always be run with a mocked scheduler (v17 or not). This PR adds a warning for the same. I'll put up a separate PR to the docs with a page detailing how to mock the scheduler.

Author: Sunil Pai

fixtures/dom/src/__tests__/nested-act-test.js

@@ -0,0 +1,97 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @emails react-core
+ */
+
+let React;
+let TestUtils;
+let TestRenderer;
+
+global.__DEV__ = process.env.NODE_ENV !== 'production';
+
+expect.extend(require('../toWarnDev'));
+
+describe('unmocked scheduler', () => {
+  beforeEach(() => {
+    jest.resetModules();
+    React = require('react');
+    TestUtils = require('react-dom/test-utils');
+    TestRenderer = require('react-test-renderer');
+  });
+
+  it('flushes work only outside the outermost act() corresponding to its own renderer', () => {
+    let log = [];
+    function Effecty() {
+      React.useEffect(() => {
+        log.push('called');
+      }, []);
+      return null;
+    }
+    // in legacy mode, this tests whether an act only flushes its own effects
+    TestRenderer.act(() => {
+      TestUtils.act(() => {
+        TestRenderer.create(<Effecty />);
+      });
+      expect(log).toEqual([]);
+    });
+    expect(log).toEqual(['called']);
+
+    log = [];
+    // for doublechecking, we flip it inside out, and assert on the outermost
+    TestUtils.act(() => {
+      TestRenderer.act(() => {
+        TestRenderer.create(<Effecty />);
+      });
+      expect(log).toEqual(['called']);
+    });
+    expect(log).toEqual(['called']);
+  });
+});
+
+describe('mocked scheduler', () => {
+  beforeEach(() => {
+    jest.resetModules();
+    jest.mock('scheduler', () =>
+      require.requireActual('scheduler/unstable_mock')
+    );
+    React = require('react');
+    TestUtils = require('react-dom/test-utils');
+    TestRenderer = require('react-test-renderer');
+  });
+
+  afterEach(() => {
+    jest.unmock('scheduler');
+  });
+
+  it('flushes work only outside the outermost act()', () => {
+    let log = [];
+    function Effecty() {
+      React.useEffect(() => {
+        log.push('called');
+      }, []);
+      return null;
+    }
+    // with a mocked scheduler, this tests whether it flushes all work only on the outermost act
+    TestRenderer.act(() => {
+      TestUtils.act(() => {
+        TestRenderer.create(<Effecty />);
+      });
+      expect(log).toEqual([]);
+    });
+    expect(log).toEqual(['called']);
+
+    log = [];
+    // for doublechecking, we flip it inside out, and assert on the outermost
+    TestUtils.act(() => {
+      TestRenderer.act(() => {
+        TestRenderer.create(<Effecty />);
+      });
+      expect(log).toEqual([]);
+    });
+    expect(log).toEqual(['called']);
+  });
+});

fixtures/dom/src/__tests__/wrong-act-test.js

@@ -0,0 +1,194 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @emails react-core
+ */
+
+let React;
+let ReactDOM;
+let ReactART;
+let ARTSVGMode;
+let ARTCurrentMode;
+let TestUtils;
+let TestRenderer;
+let ARTTest;
+
+global.__DEV__ = process.env.NODE_ENV !== 'production';
+
+expect.extend(require('../toWarnDev'));
+
+function App(props) {
+  return 'hello world';
+}
+
+beforeEach(() => {
+  jest.resetModules();
+  React = require('react');
+  ReactDOM = require('react-dom');
+  ReactART = require('react-art');
+  ARTSVGMode = require('art/modes/svg');
+  ARTCurrentMode = require('art/modes/current');
+  TestUtils = require('react-dom/test-utils');
+  TestRenderer = require('react-test-renderer');
+
+  ARTCurrentMode.setCurrent(ARTSVGMode);
+
+  ARTTest = function ARTTestComponent(props) {
+    return (
+      <ReactART.Surface width={150} height={200}>
+        <ReactART.Group>
+          <ReactART.Shape
+            d="M0,0l50,0l0,50l-50,0z"
+            fill={new ReactART.LinearGradient(['black', 'white'])}
+            key="a"
+            width={50}
+            height={50}
+            x={50}
+            y={50}
+            opacity={0.1}
+          />
+          <ReactART.Shape
+            fill="#3C5A99"
+            key="b"
+            scale={0.5}
+            x={50}
+            y={50}
+            title="This is an F"
+            cursor="pointer">
+            M64.564,38.583H54l0.008-5.834c0-3.035,0.293-4.666,4.657-4.666
+            h5.833V16.429h-9.33c-11.213,0-15.159,5.654-15.159,15.16v6.994
+            h-6.99v11.652h6.99v33.815H54V50.235h9.331L64.564,38.583z
+          </ReactART.Shape>
+        </ReactART.Group>
+      </ReactART.Surface>
+    );
+  };
+});
+
+it("doesn't warn when you use the right act + renderer: dom", () => {
+  TestUtils.act(() => {
+    TestUtils.renderIntoDocument(<App />);
+  });
+});
+
+it("doesn't warn when you use the right act + renderer: test", () => {
+  TestRenderer.act(() => {
+    TestRenderer.create(<App />);
+  });
+});
+
+it('resets correctly across renderers', () => {
+  function Effecty() {
+    React.useEffect(() => {}, []);
+    return null;
+  }
+  TestUtils.act(() => {
+    TestRenderer.act(() => {});
+    expect(() => {
+      TestRenderer.create(<Effecty />);
+    }).toWarnDev(["It looks like you're using the wrong act()"], {
+      withoutStack: true,
+    });
+  });
+});
+
+it('warns when using the wrong act version - test + dom: render', () => {
+  expect(() => {
+    TestRenderer.act(() => {
+      TestUtils.renderIntoDocument(<App />);
+    });
+  }).toWarnDev(["It looks like you're using the wrong act()"], {
+    withoutStack: true,
+  });
+});
+
+it('warns when using the wrong act version - test + dom: updates', () => {
+  let setCtr;
+  function Counter(props) {
+    const [ctr, _setCtr] = React.useState(0);
+    setCtr = _setCtr;
+    return ctr;
+  }
+  TestUtils.renderIntoDocument(<Counter />);
+  expect(() => {
+    TestRenderer.act(() => {
+      setCtr(1);
+    });
+  }).toWarnDev(["It looks like you're using the wrong act()"]);
+});
+
+it('warns when using the wrong act version - dom + test: .create()', () => {
+  expect(() => {
+    TestUtils.act(() => {
+      TestRenderer.create(<App />);
+    });
+  }).toWarnDev(["It looks like you're using the wrong act()"], {
+    withoutStack: true,
+  });
+});
+
+it('warns when using the wrong act version - dom + test: .update()', () => {
+  const root = TestRenderer.create(<App key="one" />);
+  expect(() => {
+    TestUtils.act(() => {
+      root.update(<App key="two" />);
+    });
+  }).toWarnDev(["It looks like you're using the wrong act()"], {
+    withoutStack: true,
+  });
+});
+
+it('warns when using the wrong act version - dom + test: updates', () => {
+  let setCtr;
+  function Counter(props) {
+    const [ctr, _setCtr] = React.useState(0);
+    setCtr = _setCtr;
+    return ctr;
+  }
+  TestRenderer.create(<Counter />);
+  expect(() => {
+    TestUtils.act(() => {
+      setCtr(1);
+    });
+  }).toWarnDev(["It looks like you're using the wrong act()"]);
+});
+
+it('does not warn when nesting react-act inside react-dom', () => {
+  TestUtils.act(() => {
+    TestUtils.renderIntoDocument(<ARTTest />);
+  });
+});
+
+it('does not warn when nesting react-act inside react-test-renderer', () => {
+  TestRenderer.act(() => {
+    TestRenderer.create(<ARTTest />);
+  });
+});
+
+it("doesn't warn if you use nested acts from different renderers", () => {
+  TestRenderer.act(() => {
+    TestUtils.act(() => {
+      TestRenderer.create(<App />);
+    });
+  });
+});
+
+it('warns when using createRoot() + .render', () => {
+  const root = ReactDOM.unstable_createRoot(document.createElement('div'));
+  expect(() => {
+    TestRenderer.act(() => {
+      root.render(<App />);
+    });
+  }).toWarnDev(
+    [
+      'In Concurrent or Sync modes, the "scheduler" module needs to be mocked',
+      "It looks like you're using the wrong act()",
+    ],
+    {
+      withoutStack: true,
+    }
+  );
+});