diff --git a/packages/react-reconciler/src/__tests__/ReactBatching-test.internal.js b/packages/react-reconciler/src/__tests__/ReactBatching-test.internal.js
index 55c3b2162a57c..8d7bb3e75668c 100644
--- a/packages/react-reconciler/src/__tests__/ReactBatching-test.internal.js
+++ b/packages/react-reconciler/src/__tests__/ReactBatching-test.internal.js
@@ -166,9 +166,11 @@ describe('ReactBlockingMode', () => {
       assertLog(['A1', 'B1']);
       expect(root).toMatchRenderedOutput('A1B1');
     } else {
+      // Only the second update should have flushed synchronously
       assertLog(['B1']);
       expect(root).toMatchRenderedOutput('A0B1');
 
+      // Now flush the first update
       await waitForAll(['A1']);
       expect(root).toMatchRenderedOutput('A1B1');
     }
diff --git a/packages/react-reconciler/src/__tests__/ReactCPUSuspense-test.js b/packages/react-reconciler/src/__tests__/ReactCPUSuspense-test.js
index ec6d9d619078f..3444f3f2a406a 100644
--- a/packages/react-reconciler/src/__tests__/ReactCPUSuspense-test.js
+++ b/packages/react-reconciler/src/__tests__/ReactCPUSuspense-test.js
@@ -143,6 +143,7 @@ describe('ReactSuspenseWithNoopRenderer', () => {
         </>,
       );
     });
+    // Inner contents finish in separate commit from outer
     assertLog(['Inner']);
     expect(root).toMatchRenderedOutput(
       <>
@@ -178,6 +179,7 @@ describe('ReactSuspenseWithNoopRenderer', () => {
     await act(async () => {
       root.render(<App />);
     });
+    // Inner contents finish in separate commit from outer
     assertLog(['Outer', 'Loading...', 'Inner [0]']);
     expect(root).toMatchRenderedOutput(
       <>
@@ -190,6 +192,7 @@ describe('ReactSuspenseWithNoopRenderer', () => {
     await act(async () => {
       setCount(1);
     });
+    // Entire update finishes in a single commit
     assertLog(['Outer', 'Inner [1]']);
     expect(root).toMatchRenderedOutput(
       <>
@@ -227,6 +230,7 @@ describe('ReactSuspenseWithNoopRenderer', () => {
         </>,
       );
     });
+    // Inner contents suspended, so we continue showing a fallback.
     assertLog(['Suspend! [Inner]']);
     expect(root).toMatchRenderedOutput(
       <>
@@ -276,6 +280,7 @@ describe('ReactSuspenseWithNoopRenderer', () => {
     await act(async () => {
       root.render(<App />);
     });
+    // Each level commits separately
     assertLog(['A', 'Loading B...', 'B', 'Loading C...', 'C']);
     expect(root).toMatchRenderedOutput(
       <>
diff --git a/packages/react-reconciler/src/__tests__/ReactCache-test.js b/packages/react-reconciler/src/__tests__/ReactCache-test.js
index 47a96971261fd..25e0dbebb00b3 100644
--- a/packages/react-reconciler/src/__tests__/ReactCache-test.js
+++ b/packages/react-reconciler/src/__tests__/ReactCache-test.js
@@ -219,6 +219,7 @@ describe('ReactCache', () => {
     await act(async () => {
       root.render('Bye');
     });
+    // no cleanup: cache is still retained at the root
     assertLog([]);
     expect(root).toMatchRenderedOutput('Bye');
   });
@@ -245,6 +246,7 @@ describe('ReactCache', () => {
     await act(async () => {
       root.render('Bye');
     });
+    // no cleanup: cache is still retained at the root
     assertLog([]);
     expect(root).toMatchRenderedOutput('Bye');
   });
@@ -273,6 +275,8 @@ describe('ReactCache', () => {
       root.render(<App showMore={false} />);
     });
 
+    // Even though there are two new <Cache /> trees, they should share the same
+    // data cache. So there should be only a single cache miss for A.
     assertLog(['Cache miss! [A]', 'Loading...', 'Loading...']);
     expect(root).toMatchRenderedOutput('Loading...Loading...');
 
@@ -285,6 +289,7 @@ describe('ReactCache', () => {
     await act(async () => {
       root.render('Bye');
     });
+    // no cleanup: cache is still retained at the root
     assertLog([]);
     expect(root).toMatchRenderedOutput('Bye');
   });
@@ -320,6 +325,8 @@ describe('ReactCache', () => {
     await act(async () => {
       root.render(<App showMore={true} />);
     });
+    // Even though there are two new <Cache /> trees, they should share the same
+    // data cache. So there should be only a single cache miss for A.
     assertLog(['Cache miss! [A]', 'Loading...', 'Loading...']);
     expect(root).toMatchRenderedOutput('Loading...Loading...');
 
@@ -332,6 +339,9 @@ describe('ReactCache', () => {
     await act(async () => {
       root.render('Bye');
     });
+    // cleanup occurs for the cache shared by the inner cache boundaries (which
+    // are not shared w the root because they were added in an update)
+    // note that no cache is created for the root since the cache is never accessed
     assertLog(['Cache cleanup: A [v1]']);
     expect(root).toMatchRenderedOutput('Bye');
   });
@@ -356,6 +366,8 @@ describe('ReactCache', () => {
       await act(async () => {
         root.render(<App />);
       });
+      // Even though there is a nested <Cache /> boundary, it should share the same
+      // data cache as the root. So there should be only a single cache miss for A.
       assertLog(['Cache miss! [A]', 'Loading...']);
       expect(root).toMatchRenderedOutput('Loading...');
 
@@ -368,6 +380,7 @@ describe('ReactCache', () => {
       await act(async () => {
         root.render('Bye');
       });
+      // no cleanup: cache is still retained at the root
       assertLog([]);
       expect(root).toMatchRenderedOutput('Bye');
     },
@@ -412,6 +425,7 @@ describe('ReactCache', () => {
     await act(async () => {
       root.render('Bye');
     });
+    // no cleanup: cache is still retained at the root
     assertLog([]);
     expect(root).toMatchRenderedOutput('Bye');
   });
@@ -468,6 +482,8 @@ describe('ReactCache', () => {
     await act(async () => {
       root.render('Bye!');
     });
+    // Cleanup occurs for the *second* cache instance: the first is still
+    // referenced by the root
     assertLog(['Cache cleanup: A [v2]']);
     expect(root).toMatchRenderedOutput('Bye!');
   });
@@ -549,6 +565,7 @@ describe('ReactCache', () => {
     await act(async () => {
       root.render('Bye');
     });
+    // no cleanup: cache is still retained at the root
     assertLog([]);
     expect(root).toMatchRenderedOutput('Bye');
   });
@@ -728,12 +745,14 @@ describe('ReactCache', () => {
     await act(async () => {
       resolveMostRecentTextCache('A');
     });
+    // Note that the version has updated, and the previous cache is cleared
     assertLog(['A [v2]', 'Cache cleanup: A [v1]']);
     expect(root).toMatchRenderedOutput('A [v2]');
 
     await act(async () => {
       root.render('Bye');
     });
+    // the original root cache already cleaned up when the refresh completed
     assertLog([]);
     expect(root).toMatchRenderedOutput('Bye');
   });
@@ -781,12 +800,14 @@ describe('ReactCache', () => {
     await act(async () => {
       resolveMostRecentTextCache('A');
     });
+    // Note that the version has updated, and the previous cache is cleared
     assertLog(['A [v2]']);
     expect(root).toMatchRenderedOutput('A [v2]');
 
     await act(async () => {
       root.render('Bye');
     });
+    // the original root cache already cleaned up when the refresh completed
     assertLog([]);
     expect(root).toMatchRenderedOutput('Bye');
   });
@@ -841,12 +862,15 @@ describe('ReactCache', () => {
         }),
       );
     });
+    // The root should re-render without a cache miss.
+    // The cache is not cleared up yet, since it's still reference by the root
     assertLog(['A [v2]']);
     expect(root).toMatchRenderedOutput('A [v2]');
 
     await act(async () => {
       root.render('Bye');
     });
+    // the refreshed cache boundary is unmounted and cleans up
     assertLog(['Cache cleanup: A [v2]']);
     expect(root).toMatchRenderedOutput('Bye');
   });
@@ -920,6 +944,8 @@ describe('ReactCache', () => {
     await act(async () => {
       root.render('Bye!');
     });
+    // Unmounting children releases the refreshed cache instance only; the root
+    // still retains the original cache instance used for the first render
     assertLog(['Cache cleanup: A [v3]']);
     expect(root).toMatchRenderedOutput('Bye!');
   });
@@ -967,6 +993,8 @@ describe('ReactCache', () => {
         root.render(<App showMore={true} />);
       });
 
+      // Even though there are two new <Cache /> trees, they should share the same
+      // data cache. So there should be only a single cache miss for A.
       assertLog(['Cache miss! [A]', 'Loading...', 'Loading...']);
       expect(root).toMatchRenderedOutput('Loading...Loading...');
 
@@ -1064,6 +1092,9 @@ describe('ReactCache', () => {
       await act(async () => {
         root.render('Bye!');
       });
+      // Unmounting children releases both cache boundaries, but the original
+      // cache instance (used by second boundary) is still referenced by the root.
+      // only the second cache instance is freed.
       assertLog(['Cache cleanup: A [v2]']);
       expect(root).toMatchRenderedOutput('Bye!');
     },
diff --git a/packages/react-reconciler/src/__tests__/ReactContextPropagation-test.js b/packages/react-reconciler/src/__tests__/ReactContextPropagation-test.js
index 65eccd01dddd6..49db1ea0fe159 100644
--- a/packages/react-reconciler/src/__tests__/ReactContextPropagation-test.js
+++ b/packages/react-reconciler/src/__tests__/ReactContextPropagation-test.js
@@ -339,6 +339,11 @@ describe('ReactLazyContextPropagation', () => {
       setOtherValue(1);
       setOtherValue(0);
     });
+    // NOTE: If this didn't yield anything, that indicates that we never visited
+    // the consumer during the render phase, which probably means the eager
+    // bailout mechanism kicked in. Because we're testing the _lazy_ bailout
+    // mechanism, update this test to foil the _eager_ bailout, somehow. Perhaps
+    // by switching to useReducer.
     assertLog(['Consumer']);
     expect(root).toMatchRenderedOutput('0');
   });
diff --git a/packages/react-reconciler/src/__tests__/ReactDeferredValue-test.js b/packages/react-reconciler/src/__tests__/ReactDeferredValue-test.js
index dd9053afc1c3e..328e77b1850d8 100644
--- a/packages/react-reconciler/src/__tests__/ReactDeferredValue-test.js
+++ b/packages/react-reconciler/src/__tests__/ReactDeferredValue-test.js
@@ -78,6 +78,7 @@ describe('ReactDeferredValue', () => {
       root.render(<App value={2} />);
 
       await waitForPaint(['Original: 2']);
+      // The deferred value updates in a separate render
       await waitForPaint(['Deferred: 2']);
     });
     expect(root).toMatchRenderedOutput(
@@ -92,6 +93,7 @@ describe('ReactDeferredValue', () => {
       startTransition(() => {
         root.render(<App value={3} />);
       });
+      // The deferred value updates in the same render as the original
       await waitForPaint(['Original: 3', 'Deferred: 3']);
     });
     expect(root).toMatchRenderedOutput(
@@ -137,6 +139,7 @@ describe('ReactDeferredValue', () => {
       root.render(<App value={2} />);
 
       await waitForPaint(['Original: 2']);
+      // The deferred value updates in a separate render
       await waitForPaint(['Deferred: 2']);
     });
     expect(root).toMatchRenderedOutput(
@@ -151,6 +154,7 @@ describe('ReactDeferredValue', () => {
       startTransition(() => {
         root.render(<App value={3} />);
       });
+      // The deferred value updates in the same render as the original
       await waitForPaint(['Original: 3', 'Deferred: 3']);
     });
     expect(root).toMatchRenderedOutput(
@@ -201,6 +205,7 @@ describe('ReactDeferredValue', () => {
       root.render(<App value={2} />);
 
       await waitForPaint(['Original: 2']);
+      // The deferred value updates in a separate render
       await waitForPaint(['Deferred: 2']);
     });
     expect(root).toMatchRenderedOutput(
@@ -215,6 +220,7 @@ describe('ReactDeferredValue', () => {
       startTransition(() => {
         root.render(<App value={3} />);
       });
+      // The deferred value updates in the same render as the original
       await waitForPaint(['Original: 3', 'Deferred: 3']);
     });
     expect(root).toMatchRenderedOutput(
@@ -270,6 +276,9 @@ describe('ReactDeferredValue', () => {
       startTransition(() => {
         root.render(<App value={2} />);
       });
+      // In the regression, the memoized value was not updated during non-urgent
+      // updates, so this would flip the deferred value back to the initial
+      // value (1) instead of reusing the current one (2).
       await waitForPaint(['Original: 2', 'Deferred: 2']);
       expect(root).toMatchRenderedOutput(
         <div>
diff --git a/packages/react-reconciler/src/__tests__/ReactExpiration-test.js b/packages/react-reconciler/src/__tests__/ReactExpiration-test.js
index 2556a16ac3b21..1903ab2eee25f 100644
--- a/packages/react-reconciler/src/__tests__/ReactExpiration-test.js
+++ b/packages/react-reconciler/src/__tests__/ReactExpiration-test.js
@@ -171,14 +171,17 @@ describe('ReactExpiration', () => {
     });
     // Advance the timer.
     Scheduler.unstable_advanceTime(2000);
+    // Partially flush the first update, then interrupt it.
     await waitFor(['A [render]']);
     interrupt();
 
+    // Don't advance time by enough to expire the first update.
     assertLog([]);
     expect(ReactNoop).toMatchRenderedOutput(null);
 
     // Schedule another update.
     ReactNoop.render(<TextClass text="B" />);
+    // Both updates are batched
     await waitForAll(['B [render]', 'B [commit]']);
     expect(ReactNoop).toMatchRenderedOutput(<span prop="B" />);
 
@@ -190,6 +193,8 @@ describe('ReactExpiration', () => {
     expect(ReactNoop).toMatchRenderedOutput(<span prop="B" />);
     // Schedule another update.
     ReactNoop.render(<TextClass text="B" />);
+    // The updates should flush in the same batch, since as far as the scheduler
+    // knows, they may have occurred inside the same event.
     await waitForAll(['B [render]', 'B [commit]']);
   });
 
@@ -223,14 +228,17 @@ describe('ReactExpiration', () => {
       });
       // Advance the timer.
       Scheduler.unstable_advanceTime(2000);
+      // Partially flush the first update, then interrupt it.
       await waitFor(['A [render]']);
       interrupt();
 
+      // Don't advance time by enough to expire the first update.
       assertLog([]);
       expect(ReactNoop).toMatchRenderedOutput(null);
 
       // Schedule another update.
       ReactNoop.render(<TextClass text="B" />);
+      // Both updates are batched
       await waitForAll(['B [render]', 'B [commit]']);
       expect(ReactNoop).toMatchRenderedOutput(<span prop="B" />);
 
@@ -247,6 +255,8 @@ describe('ReactExpiration', () => {
 
       // Schedule another update.
       ReactNoop.render(<TextClass text="B" />);
+      // The updates should flush in the same batch, since as far as the scheduler
+      // knows, they may have occurred inside the same event.
       await waitForAll(['B [render]', 'B [commit]']);
     },
   );
@@ -471,7 +481,9 @@ describe('ReactExpiration', () => {
       // In other words, we can flush just the first child without flushing
       // the rest.
       Scheduler.unstable_flushNumberOfYields(1);
+      // Yield right after first child.
       assertLog(['Sync pri: 1']);
+      // Now do the rest.
       await waitForAll(['Normal pri: 1']);
     });
     expect(root).toMatchRenderedOutput('Sync pri: 1, Normal pri: 1');
@@ -533,6 +545,7 @@ describe('ReactExpiration', () => {
       await waitFor(['Sync pri: 0']);
       updateSyncPri();
     });
+    // Same thing should happen as last time
     assertLog([
       // Interrupt idle update to render sync update
       'Sync pri: 1',
@@ -733,6 +746,7 @@ describe('ReactExpiration', () => {
       Scheduler.unstable_flushNumberOfYields(1);
       assertLog(['A1', 'B1', 'C1']);
     });
+    // The effect flushes after paint.
     assertLog(['Effect: 1']);
   });
 });
diff --git a/packages/react-reconciler/src/__tests__/ReactFlushSync-test.js b/packages/react-reconciler/src/__tests__/ReactFlushSync-test.js
index 4e3e948c46268..9b9d2abe35e78 100644
--- a/packages/react-reconciler/src/__tests__/ReactFlushSync-test.js
+++ b/packages/react-reconciler/src/__tests__/ReactFlushSync-test.js
@@ -52,6 +52,7 @@ describe('ReactFlushSync', () => {
       React.startTransition(() => {
         root.render(<App />);
       });
+      // This will yield right before the passive effect fires
       await waitForPaint(['0, 0']);
 
       // The passive effect will schedule a sync update and a normal update.
@@ -67,6 +68,7 @@ describe('ReactFlushSync', () => {
       if (gate(flags => flags.enableUnifiedSyncLane)) {
         await waitForPaint([]);
       } else {
+        // Now flush it.
         await waitForPaint(['1, 1']);
       }
     });
@@ -112,9 +114,11 @@ describe('ReactFlushSync', () => {
           });
         });
       });
+      // Only the sync update should have flushed
       assertLog(['1, 0']);
       expect(root).toMatchRenderedOutput('1, 0');
     });
+    // Now the async update has flushed, too.
     assertLog(['1, 1']);
     expect(root).toMatchRenderedOutput('1, 1');
   });
@@ -162,6 +166,7 @@ describe('ReactFlushSync', () => {
       ]);
       expect(root).toMatchRenderedOutput('Child');
     });
+    // Effect flushes after paint.
     assertLog(['Effect']);
   });
 
@@ -217,6 +222,7 @@ describe('ReactFlushSync', () => {
       ]);
       expect(root).toMatchRenderedOutput('Child');
     });
+    // Effect flushes after paint.
     assertLog(['Effect']);
   });
 
@@ -236,8 +242,10 @@ describe('ReactFlushSync', () => {
 
       // Passive effects are pending. Calling flushSync should not affect them.
       ReactNoop.flushSync();
+      // Effects still haven't fired.
       assertLog([]);
     });
+    // Now the effects have fired.
     assertLog(['Effect']);
   });
 });
diff --git a/packages/react-reconciler/src/__tests__/ReactFragment-test.js b/packages/react-reconciler/src/__tests__/ReactFragment-test.js
index 7de3300bf33b7..e6b9c185ca40e 100644
--- a/packages/react-reconciler/src/__tests__/ReactFragment-test.js
+++ b/packages/react-reconciler/src/__tests__/ReactFragment-test.js
@@ -944,6 +944,7 @@ describe('ReactFragment', () => {
     );
 
     ReactNoop.render(<Foo condition={false} />);
+    // The key warning gets deduped because it's in the same component.
     await waitForAll([]);
 
     expect(ops).toEqual(['Update Stateful']);
@@ -955,6 +956,7 @@ describe('ReactFragment', () => {
     );
 
     ReactNoop.render(<Foo condition={true} />);
+    // The key warning gets deduped because it's in the same component.
     await waitForAll([]);
 
     expect(ops).toEqual(['Update Stateful', 'Update Stateful']);
diff --git a/packages/react-reconciler/src/__tests__/ReactSuspenseWithNoopRenderer-test.js b/packages/react-reconciler/src/__tests__/ReactSuspenseWithNoopRenderer-test.js
index 3a268504136df..0c857c232424b 100644
--- a/packages/react-reconciler/src/__tests__/ReactSuspenseWithNoopRenderer-test.js
+++ b/packages/react-reconciler/src/__tests__/ReactSuspenseWithNoopRenderer-test.js
@@ -299,6 +299,7 @@ describe('ReactSuspenseWithNoopRenderer', () => {
 
     // Resolve the data
     await resolveText('A');
+    // Renders successfully
     await waitForAll(['Foo', 'Bar', 'A', 'B']);
     expect(ReactNoop).toMatchRenderedOutput(
       <>
@@ -375,6 +376,7 @@ describe('ReactSuspenseWithNoopRenderer', () => {
         </Suspense>,
       );
     });
+    // B suspends. Continue rendering the remaining siblings.
     await waitForAll(['A', 'Suspend! [B]', 'C', 'D', 'Loading...']);
     // Did not commit yet.
     expect(ReactNoop).toMatchRenderedOutput(null);
@@ -382,6 +384,7 @@ describe('ReactSuspenseWithNoopRenderer', () => {
     // Wait for data to resolve
     await resolveText('B');
     await waitForAll(['A', 'B', 'C', 'D']);
+    // Renders successfully
     expect(ReactNoop).toMatchRenderedOutput(
       <>
         <span prop="A" />
@@ -730,6 +733,8 @@ describe('ReactSuspenseWithNoopRenderer', () => {
     // the update.
     ReactNoop.expire(10000);
     await advanceTimers(10000);
+    // No additional rendering work is required, since we already prepared
+    // the placeholder.
     assertLog([]);
     // Should have committed the placeholder.
     expect(ReactNoop).toMatchRenderedOutput(
@@ -974,6 +979,7 @@ describe('ReactSuspenseWithNoopRenderer', () => {
     // but not by enough to flush the promise or reach the true expiration time.
     ReactNoop.expire(2000);
     await advanceTimers(2000);
+    // Even flushing won't yield a fallback in a transition.
     expect(ReactNoop).toMatchRenderedOutput(null);
 
     await waitForAll([]);
@@ -1014,6 +1020,8 @@ describe('ReactSuspenseWithNoopRenderer', () => {
 
     await resolveText('Async');
 
+    // Because we're already showing a fallback, interrupt the current render
+    // and restart immediately.
     await waitForAll(['Async', 'Sibling']);
     expect(root).toMatchRenderedOutput(
       <>
@@ -1081,6 +1089,7 @@ describe('ReactSuspenseWithNoopRenderer', () => {
 
     // Resolve the promise
     await resolveText('Async');
+    // We can now resume rendering
     await waitForAll(['Async']);
     expect(ReactNoop).toMatchRenderedOutput(<span prop="Async" />);
   });
@@ -1106,6 +1115,7 @@ describe('ReactSuspenseWithNoopRenderer', () => {
 
     // Schedule an update, and suspend for up to 5 seconds.
     React.startTransition(() => ReactNoop.render(<App text="A" />));
+    // The update should suspend.
     await waitForAll(['Suspend! [A]', 'Loading...']);
     expect(ReactNoop).toMatchRenderedOutput(<span prop="S" />);
 
@@ -1117,6 +1127,7 @@ describe('ReactSuspenseWithNoopRenderer', () => {
 
     // Schedule another low priority update.
     React.startTransition(() => ReactNoop.render(<App text="B" />));
+    // This update should also suspend.
     await waitForAll(['Suspend! [B]', 'Loading...']);
     expect(ReactNoop).toMatchRenderedOutput(<span prop="S" />);
 
@@ -1129,6 +1140,7 @@ describe('ReactSuspenseWithNoopRenderer', () => {
     // Flush the remaining work.
     await resolveText('A');
     await resolveText('B');
+    // Nothing else to render.
     await waitForAll([]);
     expect(ReactNoop).toMatchRenderedOutput(<span prop="C" />);
   });
@@ -1778,6 +1790,7 @@ describe('ReactSuspenseWithNoopRenderer', () => {
       'Commit root',
     ]);
 
+    // Flush passive effects.
     await waitForAll([
       'Effect [A]',
       // B's effect should not fire because it suspended
@@ -1823,6 +1836,7 @@ describe('ReactSuspenseWithNoopRenderer', () => {
       'Commit root',
     ]);
 
+    // Flush passive effects.
     await waitForAll([
       // B2's effect should not fire because it suspended
       // 'Effect [B2]',
@@ -1863,6 +1877,7 @@ describe('ReactSuspenseWithNoopRenderer', () => {
     });
     Scheduler.unstable_advanceTime(100);
     await advanceTimers(100);
+    // Start rendering
     await waitFor(['Foo']);
     // For some reason it took a long time to render Foo.
     Scheduler.unstable_advanceTime(1250);
@@ -1878,12 +1893,15 @@ describe('ReactSuspenseWithNoopRenderer', () => {
     // Flush some of the time
     Scheduler.unstable_advanceTime(450);
     await advanceTimers(450);
+    // Because we've already been waiting for so long we can
+    // wait a bit longer. Still nothing...
     await waitForAll([]);
     expect(ReactNoop).toMatchRenderedOutput(null);
 
     // Eventually we'll show the fallback.
     Scheduler.unstable_advanceTime(500);
     await advanceTimers(500);
+    // No need to rerender.
     await waitForAll([]);
     // Since this is a transition, we never fallback.
     expect(ReactNoop).toMatchRenderedOutput(null);
@@ -1891,6 +1909,8 @@ describe('ReactSuspenseWithNoopRenderer', () => {
     // Flush the promise completely
     await resolveText('A');
     await waitForAll(['Foo', 'A']);
+    // Renders successfully
+    // TODO: Why does this render Foo
     expect(ReactNoop).toMatchRenderedOutput(<span prop="A" />);
   });
 
@@ -1909,6 +1929,7 @@ describe('ReactSuspenseWithNoopRenderer', () => {
     }
 
     ReactNoop.render(<Foo />);
+    // Start rendering
     await waitForAll([
       'Foo',
       // A suspends
@@ -1925,6 +1946,7 @@ describe('ReactSuspenseWithNoopRenderer', () => {
     Scheduler.unstable_advanceTime(5000);
     await advanceTimers(5000);
 
+    // Retry with the new content.
     await waitForAll([
       'A',
       // B still suspends
@@ -1943,6 +1965,7 @@ describe('ReactSuspenseWithNoopRenderer', () => {
 
     // Flush the last promise completely
     await resolveText('B');
+    // Renders successfully
     await waitForAll(['B']);
     expect(ReactNoop).toMatchRenderedOutput(
       <>
@@ -1967,6 +1990,7 @@ describe('ReactSuspenseWithNoopRenderer', () => {
     }
 
     ReactNoop.render(<Foo />);
+    // Start rendering
     await waitForAll([
       'Foo',
       // A suspends
@@ -1980,6 +2004,7 @@ describe('ReactSuspenseWithNoopRenderer', () => {
 
     await resolveText('A');
 
+    // Retry with the new content.
     await waitForAll([
       'A',
       // B still suspends
@@ -1995,6 +2020,7 @@ describe('ReactSuspenseWithNoopRenderer', () => {
     // Before we commit another Promise resolves.
     // We're still showing the first loading state.
     expect(ReactNoop).toMatchRenderedOutput(<span prop="Loading..." />);
+    // Restart and render the complete content.
     await waitForAll(['A', 'B']);
     expect(ReactNoop).toMatchRenderedOutput(
       <>
@@ -2040,6 +2066,10 @@ describe('ReactSuspenseWithNoopRenderer', () => {
     Scheduler.unstable_advanceTime(500);
     jest.advanceTimersByTime(500);
 
+    // We should have already shown the fallback.
+    // When we wrote this test, we inferred the start time of high priority
+    // updates as way earlier in the past. This test ensures that we don't
+    // use this assumption to add a very long JND.
     await waitForAll([]);
     // Transitions never fallback.
     expect(ReactNoop).toMatchRenderedOutput(null);
@@ -2481,6 +2511,7 @@ describe('ReactSuspenseWithNoopRenderer', () => {
 
     // Schedule an update at idle pri.
     ReactNoop.idleUpdates(() => ReactNoop.render(<Foo renderContent={2} />));
+    // We won't even work on Idle priority.
     await waitForAll([]);
 
     // We're still suspended.
@@ -3040,6 +3071,9 @@ describe('ReactSuspenseWithNoopRenderer', () => {
     await act(async () => {
       foo.setState({suspend: true});
 
+      // In the regression that this covers, we would neglect to reset the
+      // current debug phase after suspending (in the catch block), so React
+      // thinks we're still inside the render phase.
       await waitFor(['Suspend!']);
 
       // Then when this setState happens, React would incorrectly fire a warning
@@ -3130,6 +3164,7 @@ describe('ReactSuspenseWithNoopRenderer', () => {
     await waitFor(['Commit']);
     expect(ReactNoop).toMatchRenderedOutput(<div hidden={true} />);
 
+    // Partially render through the hidden content.
     await waitFor(['Suspend! [A]']);
 
     // Start transition.
@@ -3270,6 +3305,7 @@ describe('ReactSuspenseWithNoopRenderer', () => {
           </>,
         );
 
+        // Now flush the remaining work. The Idle update successfully finishes.
         await waitForAll(['C']);
         expect(root).toMatchRenderedOutput(<span prop="C" />);
       });
@@ -3433,6 +3469,8 @@ describe('ReactSuspenseWithNoopRenderer', () => {
       await act(async () => {
         setText('D');
       });
+      // Even though the fragment fiber is not part of the return path, we should
+      // be able to finish rendering.
       assertLog(['D']);
       expect(root).toMatchRenderedOutput(<span prop="D" />);
     },
@@ -3513,6 +3551,8 @@ describe('ReactSuspenseWithNoopRenderer', () => {
           setText('E');
         });
       });
+      // Even though the fragment fiber is not part of the return path, we should
+      // be able to finish rendering.
       assertLog(['Suspend! [D]', 'E']);
       expect(root).toMatchRenderedOutput(<span prop="E" />);
     },
@@ -3622,6 +3662,9 @@ describe('ReactSuspenseWithNoopRenderer', () => {
         });
       });
 
+      // Only the outer part can update. The inner part should still show a
+      // fallback because we haven't finished loading B yet. Otherwise, the
+      // inner text would be inconsistent with the outer text.
       assertLog([
         'Outer text: B',
         'Outer step: 1',
@@ -3882,11 +3925,14 @@ describe('ReactSuspenseWithNoopRenderer', () => {
       ReactNoop.idleUpdates(() => {
         setText('B');
       });
+      // Suspend the first update. The second update doesn't run because it has
+      // Idle priority.
       await waitForAll(['Suspend! [B]', 'Loading...']);
 
       // Commit the fallback. Now we'll try working on Idle.
       jest.runAllTimers();
 
+      // It also suspends.
       await waitForAll(['Suspend! [B]']);
     });
 
@@ -3934,6 +3980,7 @@ describe('ReactSuspenseWithNoopRenderer', () => {
       // Before the retry happens, schedule a new update.
       setText('B');
 
+      // The update should be allowed to finish before the retry is attempted.
       await waitForPaint(['B']);
       expect(root).toMatchRenderedOutput(
         <>
@@ -3942,6 +3989,7 @@ describe('ReactSuspenseWithNoopRenderer', () => {
         </>,
       );
     });
+    // Then do the retry.
     assertLog(['Async']);
     expect(root).toMatchRenderedOutput(
       <>