react-next.diff

diff --git a/babel.config.js b/babel.config.js
index ac044fb372..4d59b97096 100644
--- a/babel.config.js
+++ b/babel.config.js
@@ -41,7 +41,13 @@ module.exports = function getBabelConfig(api) {
         shippedProposals: api.env('modern'),
       },
     ],
-    '@babel/preset-react',
+    [
+      '@babel/preset-react',
+      {
+        // default in Babel 8
+        runtime: 'automatic',
+      },
+    ],
     '@babel/preset-typescript',
   ];

diff --git a/packages/material-ui-styles/src/ThemeProvider/ThemeProvider.test.js b/packages/material-ui-styles/src/ThemeProvider/ThemeProvider.test.js
index 197b2f77a3..f1ead08079 100644
--- a/packages/material-ui-styles/src/ThemeProvider/ThemeProvider.test.js
+++ b/packages/material-ui-styles/src/ThemeProvider/ThemeProvider.test.js
@@ -127,11 +127,7 @@ describe('ThemeProvider', () => {
             <div />
           </ThemeProvider>,
         );
-      }).toErrorDev([
-        'However, no outer theme is present.',
-        // strict mode renders twice
-        'However, no outer theme is present.',
-      ]);
+      }).toErrorDev(['However, no outer theme is present.']);
     });
 
     it('should warn about wrong theme function', () => {
@@ -144,11 +140,7 @@ describe('ThemeProvider', () => {
             ,
           </ThemeProvider>,
         );
-      }).toErrorDev([
-        'Material-UI: You should return an object from your theme function',
-        // strict mode renders twice
-        'Material-UI: You should return an object from your theme function',
-      ]);
+      }).toErrorDev(['Material-UI: You should return an object from your theme function']);
     });
   });
 });
diff --git a/packages/material-ui-styles/src/useThemeVariants/useThemeVariants.test.js b/packages/material-ui-styles/src/useThemeVariants/useThemeVariants.test.js
index 2ab151c6c8..6db6326d77 100644
--- a/packages/material-ui-styles/src/useThemeVariants/useThemeVariants.test.js
+++ b/packages/material-ui-styles/src/useThemeVariants/useThemeVariants.test.js
@@ -135,11 +135,6 @@ describe('useThemeVariants', () => {
         </ThemeProvider>,
       ),
     ).toErrorDev([
-      // strict mode renders twice
-      [
-        `Material-UI: You are using a variant value \`test\` for which you didn't define styles.`,
-        `Please create a new variant matcher in your theme for this variant. To learn more about matchers visit https://next.material-ui.com/r/custom-component-variants.`,
-      ].join('\n'),
       [
         `Material-UI: You are using a variant value \`test\` for which you didn't define styles.`,
         `Please create a new variant matcher in your theme for this variant. To learn more about matchers visit https://next.material-ui.com/r/custom-component-variants.`,
diff --git a/packages/material-ui/src/Autocomplete/Autocomplete.test.js b/packages/material-ui/src/Autocomplete/Autocomplete.test.js
index 07345638e7..acfecbdf3e 100644
--- a/packages/material-ui/src/Autocomplete/Autocomplete.test.js
+++ b/packages/material-ui/src/Autocomplete/Autocomplete.test.js
@@ -1176,8 +1176,6 @@ describe('<Autocomplete />', () => {
         fireEvent.change(textbox, { target: { value: 'a' } });
         fireEvent.keyDown(textbox, { key: 'Enter' });
       }).toErrorDev([
-        'Material-UI: The `getOptionLabel` method of Autocomplete returned undefined instead of a string',
-        // strict mode renders twice
         'Material-UI: The `getOptionLabel` method of Autocomplete returned undefined instead of a string',
         'Material-UI: The `getOptionLabel` method of Autocomplete returned undefined instead of a string',
         'Material-UI: The `getOptionLabel` method of Autocomplete returned undefined instead of a string',
@@ -1232,9 +1230,6 @@ describe('<Autocomplete />', () => {
           />,
         );
       }).toWarnDev([
-        'None of the options match with `"not a good value"`',
-        // strict mode renders twice
-        'None of the options match with `"not a good value"`',
         'None of the options match with `"not a good value"`',
         'None of the options match with `"not a good value"`',
       ]);
@@ -1260,11 +1255,7 @@ describe('<Autocomplete />', () => {
             groupBy={(option) => option.group}
           />,
         );
-      }).toWarnDev([
-        // strict mode renders twice
-        'returns duplicated headers',
-        'returns duplicated headers',
-      ]);
+      }).toWarnDev(['returns duplicated headers']);
       const options = screen.getAllByRole('option').map((el) => el.textContent);
       expect(options).to.have.length(7);
       expect(options).to.deep.equal(['A', 'D', 'E', 'B', 'G', 'F', 'C']);
diff --git a/packages/material-ui/src/Breadcrumbs/Breadcrumbs.test.js b/packages/material-ui/src/Breadcrumbs/Breadcrumbs.test.js
index d5c5735ecf..86a4ebdece 100644
--- a/packages/material-ui/src/Breadcrumbs/Breadcrumbs.test.js
+++ b/packages/material-ui/src/Breadcrumbs/Breadcrumbs.test.js
@@ -100,7 +100,6 @@ describe('<Breadcrumbs />', () => {
       );
     }).toErrorDev([
       'Material-UI: You have provided an invalid combination of props to the Breadcrumbs.\nitemsAfterCollapse={2} + itemsBeforeCollapse={2} >= maxItems={3}',
-      'Material-UI: You have provided an invalid combination of props to the Breadcrumbs.\nitemsAfterCollapse={2} + itemsBeforeCollapse={2} >= maxItems={3}',
     ]);
     expect(screen.getAllByRole('listitem', { hidden: false })).to.have.length(4);
     expect(screen.getByRole('list')).to.have.text('first/second/third/fourth');
diff --git a/packages/material-ui/src/ClickAwayListener/ClickAwayListener.test.js b/packages/material-ui/src/ClickAwayListener/ClickAwayListener.test.js
index d78203151f..72ac37571b 100644
--- a/packages/material-ui/src/ClickAwayListener/ClickAwayListener.test.js
+++ b/packages/material-ui/src/ClickAwayListener/ClickAwayListener.test.js
@@ -132,8 +132,7 @@ describe('<ClickAwayListener />', () => {
       expect(handleClickAway.callCount).to.equal(0);
 
       fireEvent.click(getByText('Stop inside a portal'));
-      // True-negative, we don't have enough information to do otherwise.
-      expect(handleClickAway.callCount).to.equal(1);
+      expect(handleClickAway.callCount).to.equal(0);
     });
   });
 
diff --git a/packages/material-ui/src/Tabs/Tabs.test.js b/packages/material-ui/src/Tabs/Tabs.test.js
index d629210cde..f53f50970f 100644
--- a/packages/material-ui/src/Tabs/Tabs.test.js
+++ b/packages/material-ui/src/Tabs/Tabs.test.js
@@ -90,9 +90,6 @@ describe('<Tabs />', () => {
       expect(() => {
         render(<Tabs value={0} centered variant="scrollable" />);
       }).toErrorDev([
-        'Material-UI: You can not use the `centered={true}` and `variant="scrollable"`',
-        // StrictMode renders twice
-        'Material-UI: You can not use the `centered={true}` and `variant="scrollable"`',
         'Material-UI: You can not use the `centered={true}` and `variant="scrollable"`',
         'Material-UI: You can not use the `centered={true}` and `variant="scrollable"`',
       ]);
diff --git a/packages/material-ui/src/TextareaAutosize/TextareaAutosize.test.js b/packages/material-ui/src/TextareaAutosize/TextareaAutosize.test.js
index 9cd267a0c0..7323483c87 100644
--- a/packages/material-ui/src/TextareaAutosize/TextareaAutosize.test.js
+++ b/packages/material-ui/src/TextareaAutosize/TextareaAutosize.test.js
@@ -255,12 +255,7 @@ describe('<TextareaAutosize />', () => {
 
         expect(() => {
           forceUpdate();
-        }).toErrorDev([
-          'Material-UI: Too many re-renders.',
-          // strict mode renders twice
-          'Material-UI: Too many re-renders.',
-          'Material-UI: Too many re-renders.',
-        ]);
+        }).toErrorDev(['Material-UI: Too many re-renders.']);
       });
     });
   });
diff --git a/packages/material-ui/src/internal/SwitchBase.test.js b/packages/material-ui/src/internal/SwitchBase.test.js
index 8c8f59a9d8..657a5e57bc 100644
--- a/packages/material-ui/src/internal/SwitchBase.test.js
+++ b/packages/material-ui/src/internal/SwitchBase.test.js
@@ -366,7 +366,7 @@ describe('<SwitchBase />', () => {
         setProps({ checked: true });
         global['didWarnControlledToUncontrolled'] = true;
       }).toErrorDev([
-        'Warning: A component is changing an uncontrolled input of type checkbox to be controlled.',
+        'Warning: A component is changing an uncontrolled input to be controlled.',
         'Material-UI: A component is changing the uncontrolled checked state of SwitchBase to be controlled.',
       ]);
     });
@@ -387,7 +387,7 @@ describe('<SwitchBase />', () => {
         setProps({ checked: undefined });
         global['didWarnControlledToUncontrolled'] = true;
       }).toErrorDev([
-        'Warning: A component is changing a controlled input of type checkbox to be uncontrolled.',
+        'Warning: A component is changing a controlled input to be uncontrolled',
         'Material-UI: A component is changing the controlled checked state of SwitchBase to be uncontrolled.',
       ]);
     });
diff --git a/packages/material-ui/src/useMediaQuery/useMediaQuery.test.js b/packages/material-ui/src/useMediaQuery/useMediaQuery.test.js
index 25dc48c4c1..b33af6309c 100644
--- a/packages/material-ui/src/useMediaQuery/useMediaQuery.test.js
+++ b/packages/material-ui/src/useMediaQuery/useMediaQuery.test.js
@@ -277,11 +277,7 @@ describe('useMediaQuery', () => {
 
       expect(() => {
         render(<MyComponent />);
-      }).toErrorDev([
-        'Material-UI: The `query` argument provided is invalid',
-        // logs warning twice in StrictMode
-        'Material-UI: The `query` argument provided is invalid',
-      ]);
+      }).toErrorDev(['Material-UI: The `query` argument provided is invalid']);
     });
   });
 });