diff --git a/packages/docusaurus/src/server/__tests__/__snapshots__/configValidation.test.ts.snap b/packages/docusaurus/src/server/__tests__/__snapshots__/configValidation.test.ts.snap
index 6dca123a95076..d298a46eb83d9 100644
--- a/packages/docusaurus/src/server/__tests__/__snapshots__/configValidation.test.ts.snap
+++ b/packages/docusaurus/src/server/__tests__/__snapshots__/configValidation.test.ts.snap
@@ -1,6 +1,30 @@
 // Jest Snapshot v1, https://goo.gl/fbAQLP
 
-exports[`normalizeConfig should throw error if plugins is not a string and it's not an array #1 for the input of: [123] 1`] = `
+exports[`normalizeConfig throws error for required fields 1`] = `
+""baseUrl" is required
+"title" is required
+"url" is required
+"themes" must be an array
+"presets" must be an array
+"scripts" must be an array
+"stylesheets" must be an array
+These field(s) ("invalidField",) are not recognized in docusaurus.config.js.
+If you still want these fields to be in your configuration, put them in the "customFields" field.
+See https://docusaurus.io/docs/api/docusaurus-config/#customfields"
+`;
+
+exports[`normalizeConfig throws error for unknown field 1`] = `
+"These field(s) ("invalid",) are not recognized in docusaurus.config.js.
+If you still want these fields to be in your configuration, put them in the "customFields" field.
+See https://docusaurus.io/docs/api/docusaurus-config/#customfields"
+`;
+
+exports[`onBrokenLinks throws for "error" reporting severity 1`] = `
+""onBrokenLinks" must be one of [ignore, log, warn, throw]
+"
+`;
+
+exports[`plugins should throw error if plugins is not a string and it's not an array #1 for the input of: [123] 1`] = `
 " => Bad Docusaurus plugin value plugins[0].
 Example valid plugin config:
 {
@@ -16,7 +40,7 @@ Example valid plugin config:
 "
 `;
 
-exports[`normalizeConfig should throw error if plugins is not an array of [string, object][] #1 for the input of: [[Array]] 1`] = `
+exports[`plugins should throw error if plugins is not an array of [string, object][] #1 for the input of: [[Array]] 1`] = `
 " => Bad Docusaurus plugin value plugins[0].
 Example valid plugin config:
 {
@@ -32,7 +56,7 @@ Example valid plugin config:
 "
 `;
 
-exports[`normalizeConfig should throw error if plugins is not an array of [string, object][] #2 for the input of: [[Array]] 1`] = `
+exports[`plugins should throw error if plugins is not an array of [string, object][] #2 for the input of: [[Array]] 1`] = `
 " => Bad Docusaurus plugin value plugins[0].
 Example valid plugin config:
 {
@@ -48,7 +72,7 @@ Example valid plugin config:
 "
 `;
 
-exports[`normalizeConfig should throw error if plugins is not an array of [string, object][] #3 for the input of: [[Array]] 1`] = `
+exports[`plugins should throw error if plugins is not an array of [string, object][] #3 for the input of: [[Array]] 1`] = `
 " => Bad Docusaurus plugin value plugins[0].
 Example valid plugin config:
 {
@@ -64,12 +88,12 @@ Example valid plugin config:
 "
 `;
 
-exports[`normalizeConfig should throw error if plugins is not array for the input of: {} 1`] = `
+exports[`plugins should throw error if plugins is not array for the input of: {} 1`] = `
 ""plugins" must be an array
 "
 `;
 
-exports[`normalizeConfig should throw error if themes is not a string and it's not an array #1 for the input of: [123] 1`] = `
+exports[`themes should throw error if themes is not a string and it's not an array #1 for the input of: [123] 1`] = `
 " => Bad Docusaurus theme value themes[0].
 Example valid theme config:
 {
@@ -85,7 +109,7 @@ Example valid theme config:
 "
 `;
 
-exports[`normalizeConfig should throw error if themes is not an array of [string, object][] #1 for the input of: [[Array]] 1`] = `
+exports[`themes should throw error if themes is not an array of [string, object][] #1 for the input of: [[Array]] 1`] = `
 " => Bad Docusaurus theme value themes[0].
 Example valid theme config:
 {
@@ -101,7 +125,7 @@ Example valid theme config:
 "
 `;
 
-exports[`normalizeConfig should throw error if themes is not an array of [string, object][] #2 for the input of: [[Array]] 1`] = `
+exports[`themes should throw error if themes is not an array of [string, object][] #2 for the input of: [[Array]] 1`] = `
 " => Bad Docusaurus theme value themes[0].
 Example valid theme config:
 {
@@ -117,7 +141,7 @@ Example valid theme config:
 "
 `;
 
-exports[`normalizeConfig should throw error if themes is not an array of [string, object][] #3 for the input of: [[Array]] 1`] = `
+exports[`themes should throw error if themes is not an array of [string, object][] #3 for the input of: [[Array]] 1`] = `
 " => Bad Docusaurus theme value themes[0].
 Example valid theme config:
 {
@@ -133,31 +157,7 @@ Example valid theme config:
 "
 `;
 
-exports[`normalizeConfig should throw error if themes is not array for the input of: {} 1`] = `
+exports[`themes should throw error if themes is not array for the input of: {} 1`] = `
 ""themes" must be an array
 "
 `;
-
-exports[`normalizeConfig throws error for required fields 1`] = `
-""baseUrl" is required
-"title" is required
-"url" is required
-"themes" must be an array
-"presets" must be an array
-"scripts" must be an array
-"stylesheets" must be an array
-These field(s) ("invalidField",) are not recognized in docusaurus.config.js.
-If you still want these fields to be in your configuration, put them in the "customFields" field.
-See https://docusaurus.io/docs/api/docusaurus-config/#customfields"
-`;
-
-exports[`normalizeConfig throws error for unknown field 1`] = `
-"These field(s) ("invalid",) are not recognized in docusaurus.config.js.
-If you still want these fields to be in your configuration, put them in the "customFields" field.
-See https://docusaurus.io/docs/api/docusaurus-config/#customfields"
-`;
-
-exports[`normalizeConfig throws for "error" reporting severity 1`] = `
-""onBrokenLinks" must be one of [ignore, log, warn, throw]
-"
-`;
diff --git a/packages/docusaurus/src/server/__tests__/configValidation.test.ts b/packages/docusaurus/src/server/__tests__/configValidation.test.ts
index 3fb607deba47f..b6d210a3ba66d 100644
--- a/packages/docusaurus/src/server/__tests__/configValidation.test.ts
+++ b/packages/docusaurus/src/server/__tests__/configValidation.test.ts
@@ -12,7 +12,7 @@ import {
   validateConfig,
 } from '../configValidation';
 import type {StorageConfig} from '@docusaurus/types/src/config';
-import type {Config, DocusaurusConfig} from '@docusaurus/types';
+import type {Config, DocusaurusConfig, PluginConfig} from '@docusaurus/types';
 import type {DeepPartial} from 'utility-types';
 
 const baseConfig = {
@@ -114,6 +114,34 @@ describe('normalizeConfig', () => {
     }).toThrowErrorMatchingSnapshot();
   });
 
+  it('throws error for required fields', () => {
+    expect(() =>
+      validateConfig(
+        {
+          invalidField: true,
+          presets: {},
+          stylesheets: {},
+          themes: {},
+          scripts: {},
+        },
+        'docusaurus.config.js',
+      ),
+    ).toThrowErrorMatchingSnapshot();
+  });
+});
+
+describe('config warning and error', () => {
+  function getWarning(config: unknown) {
+    return ConfigSchema.validate(config).warning;
+  }
+
+  it('baseConfig has no warning', () => {
+    const warning = getWarning(baseConfig);
+    expect(warning).toBeUndefined();
+  });
+});
+
+describe('url', () => {
   it('throws for non-string URLs', () => {
     expect(() =>
       normalizeConfig({
@@ -180,195 +208,19 @@ describe('normalizeConfig', () => {
     ).toBe('/noSlash/foo/');
   });
 
-  it.each([
-    ['should throw error if plugins is not array', {}],
-    [
-      "should throw error if plugins is not a string and it's not an array #1",
-      [123],
-    ],
-    [
-      'should throw error if plugins is not an array of [string, object][] #1',
-      [['example/path', 'wrong parameter here']],
-    ],
-    [
-      'should throw error if plugins is not an array of [string, object][] #2',
-      [[{}, 'example/path']],
-    ],
-    [
-      'should throw error if plugins is not an array of [string, object][] #3',
-      [[{}, {}]],
-    ],
-  ])(`%s for the input of: %p`, (_message, plugins) => {
-    expect(() => {
-      normalizeConfig({
-        // @ts-expect-error: test
-        plugins,
-      });
-    }).toThrowErrorMatchingSnapshot();
-  });
-
-  it.each([
-    ['should throw error if themes is not array', {}],
-    [
-      "should throw error if themes is not a string and it's not an array #1",
-      [123],
-    ],
-    [
-      'should throw error if themes is not an array of [string, object][] #1',
-      [['example/path', 'wrong parameter here']],
-    ],
-    [
-      'should throw error if themes is not an array of [string, object][] #2',
-      [[{}, 'example/path']],
-    ],
-    [
-      'should throw error if themes is not an array of [string, object][] #3',
-      [[{}, {}]],
-    ],
-  ])(`%s for the input of: %p`, (_message, themes) => {
-    expect(() => {
-      normalizeConfig({
-        // @ts-expect-error: test
-        themes,
-      });
-    }).toThrowErrorMatchingSnapshot();
-  });
-
-  it.each([
-    ['should accept [string] for plugins', ['plain/string']],
-    [
-      'should accept string[] for plugins',
-      ['plain/string', 'another/plain/string/path'],
-    ],
-    [
-      'should accept [string, object] for plugins',
-      [['plain/string', {it: 'should work'}]],
-    ],
-    [
-      'should accept [string, object][] for plugins',
-      [
-        ['plain/string', {it: 'should work'}],
-        ['this/should/work', {too: 'yes'}],
-      ],
-    ],
-    [
-      'should accept ([string, object]|string)[] for plugins',
-      [
-        'plain/string',
-        ['plain', {it: 'should work'}],
-        ['this/should/work', {too: 'yes'}],
-      ],
-    ],
-    ['should accept function for plugin', [function plugin() {}]],
-    [
-      'should accept [function, object] for plugin',
-      [[() => {}, {it: 'should work'}]],
-    ],
-    ['should accept false/null for plugin', [false as const, null, 'classic']],
-  ])(`%s for the input of: %p`, (_message, plugins) => {
-    expect(() => {
-      normalizeConfig({
-        plugins,
-      } as Config);
-    }).not.toThrow();
-  });
-
-  it.each([
-    ['should accept [string] for themes', ['plain/string']],
-    [
-      'should accept string[] for themes',
-      ['plain/string', 'another/plain/string/path'],
-    ],
-    [
-      'should accept [string, object] for themes',
-      [['plain/string', {it: 'should work'}]],
-    ],
-    [
-      'should accept [string, object][] for themes',
-      [
-        ['plain/string', {it: 'should work'}],
-        ['this/should/work', {too: 'yes'}],
-      ],
-    ],
-    [
-      'should accept ([string, object]|string)[] for themes',
-      [
-        'plain/string',
-        ['plain', {it: 'should work'}],
-        ['this/should/work', {too: 'yes'}],
-      ],
-    ],
-    ['should accept function for theme', [function theme() {}]],
-    [
-      'should accept [function, object] for theme',
-      [[function theme() {}, {it: 'should work'}]],
-    ],
-    ['should accept false/null for themes', [false, null, 'classic']],
-  ])(`%s for the input of: %p`, (_message, themes) => {
-    expect(() => {
-      normalizeConfig({
-        themes,
-      } as Config);
-    }).not.toThrow();
-  });
-
-  it('throws error if themes is not array', () => {
-    expect(() => {
-      normalizeConfig({
-        // @ts-expect-error: test
-        themes: {},
-      });
-    }).toThrowErrorMatchingInlineSnapshot(`
-      ""themes" must be an array
-      "
-    `);
-  });
-
-  it('throws error if presets is not array', () => {
-    expect(() => {
-      normalizeConfig({
-        // @ts-expect-error: test
-        presets: {},
-      });
-    }).toThrowErrorMatchingInlineSnapshot(`
-      ""presets" must be an array
-      "
-    `);
-  });
-
-  it('throws error if presets looks invalid', () => {
-    expect(() => {
-      normalizeConfig({
-        // @ts-expect-error: test
-        presets: [() => {}],
-      });
-    }).toThrowErrorMatchingInlineSnapshot(`
-      ""presets[0]" does not look like a valid preset config. A preset config entry should be one of:
-      - A tuple of [presetName, options], like \`["classic", { blog: false }]\`, or
-      - A simple string, like \`"classic"\`
-      "
-    `);
-  });
-
-  it('accepts presets as false / null', () => {
-    expect(() => {
-      normalizeConfig({
-        presets: [false, null, 'classic'],
-      });
-    }).not.toThrow();
-  });
-
-  it("throws error if scripts doesn't have src", () => {
-    expect(() => {
-      normalizeConfig({
-        scripts: ['https://some.com', {}],
-      });
-    }).toThrowErrorMatchingInlineSnapshot(`
-      ""scripts[1]" is invalid. A script must be a plain string (the src), or an object with at least a "src" property.
-      "
-    `);
+  it('site url fails validation when using subpath', () => {
+    const {error} = ConfigSchema.validate({
+      ...baseConfig,
+      url: 'https://mysite.com/someSubpath',
+    });
+    expect(error).toBeDefined();
+    expect(error?.message).toBe(
+      'The url is not supposed to contain a sub-path like "/someSubpath". Please use the baseUrl field for sub-paths.',
+    );
   });
+});
 
+describe('headTags', () => {
   it('accepts headTags with tagName and attributes', () => {
     expect(() => {
       normalizeConfig({
@@ -436,7 +288,9 @@ describe('normalizeConfig', () => {
       "
     `);
   });
+});
 
+describe('css', () => {
   it("throws error if css doesn't have href", () => {
     expect(() => {
       normalizeConfig({
@@ -447,22 +301,22 @@ describe('normalizeConfig', () => {
       "
     `);
   });
+});
 
-  it('throws error for required fields', () => {
-    expect(() =>
-      validateConfig(
-        {
-          invalidField: true,
-          presets: {},
-          stylesheets: {},
-          themes: {},
-          scripts: {},
-        },
-        'docusaurus.config.js',
-      ),
-    ).toThrowErrorMatchingSnapshot();
+describe('scripts', () => {
+  it("throws error if scripts doesn't have src", () => {
+    expect(() => {
+      normalizeConfig({
+        scripts: ['https://some.com', {}],
+      });
+    }).toThrowErrorMatchingInlineSnapshot(`
+      ""scripts[1]" is invalid. A script must be a plain string (the src), or an object with at least a "src" property.
+      "
+    `);
   });
+});
 
+describe('onBrokenLinks', () => {
   it('throws for "error" reporting severity', () => {
     expect(() =>
       validateConfig(
@@ -478,28 +332,6 @@ describe('normalizeConfig', () => {
   });
 });
 
-describe('config warning and error', () => {
-  function getWarning(config: unknown) {
-    return ConfigSchema.validate(config).warning;
-  }
-
-  it('baseConfig has no warning', () => {
-    const warning = getWarning(baseConfig);
-    expect(warning).toBeUndefined();
-  });
-
-  it('site url fails validation when using subpath', () => {
-    const {error} = ConfigSchema.validate({
-      ...baseConfig,
-      url: 'https://mysite.com/someSubpath',
-    });
-    expect(error).toBeDefined();
-    expect(error?.message).toBe(
-      'The url is not supposed to contain a sub-path like "/someSubpath". Please use the baseUrl field for sub-paths.',
-    );
-  });
-});
-
 describe('markdown', () => {
   it('accepts undefined object', () => {
     expect(
@@ -597,8 +429,14 @@ describe('markdown', () => {
   });
 
   it('throw for bad markdown format', () => {
-    expect(() => normalizeConfig({markdown: {format: null}}))
-      .toThrowErrorMatchingInlineSnapshot(`
+    expect(() =>
+      normalizeConfig({
+        markdown: {
+          // @ts-expect-error: bad value
+          format: null,
+        },
+      }),
+    ).toThrowErrorMatchingInlineSnapshot(`
       ""markdown.format" must be one of [mdx, md, detect]
       "markdown.format" must be a string
       "
@@ -617,6 +455,7 @@ describe('markdown', () => {
   it('throw for null object', () => {
     expect(() => {
       normalizeConfig({
+        // @ts-expect-error: bad value
         markdown: null,
       });
     }).toThrowErrorMatchingInlineSnapshot(`
@@ -626,6 +465,245 @@ describe('markdown', () => {
   });
 });
 
+describe('plugins', () => {
+  // Only here to verify typing
+  function ensurePlugins(plugins: PluginConfig[]): PluginConfig[] {
+    return plugins;
+  }
+
+  it.each([
+    ['should throw error if plugins is not array', {}],
+    [
+      "should throw error if plugins is not a string and it's not an array #1",
+      [123],
+    ],
+    [
+      'should throw error if plugins is not an array of [string, object][] #1',
+      [['example/path', 'wrong parameter here']],
+    ],
+    [
+      'should throw error if plugins is not an array of [string, object][] #2',
+      [[{}, 'example/path']],
+    ],
+    [
+      'should throw error if plugins is not an array of [string, object][] #3',
+      [[{}, {}]],
+    ],
+  ])(`%s for the input of: %p`, (_message, plugins) => {
+    expect(() => {
+      normalizeConfig({
+        // @ts-expect-error: test
+        plugins,
+      });
+    }).toThrowErrorMatchingSnapshot();
+  });
+
+  it.each([
+    ['should accept [string] for plugins', ensurePlugins(['plain/string'])],
+    [
+      'should accept string[] for plugins',
+      ensurePlugins(['plain/string', 'another/plain/string/path']),
+    ],
+    [
+      'should accept [string, object] for plugins',
+      ensurePlugins([['plain/string', {it: 'should work'}]]),
+    ],
+    [
+      'should accept [string, object][] for plugins',
+      ensurePlugins([
+        ['plain/string', {it: 'should work'}],
+        ['this/should/work', {too: 'yes'}],
+      ]),
+    ],
+    [
+      'should accept ([string, object]|string)[] for plugins',
+      ensurePlugins([
+        'plain/string',
+        ['plain', {it: 'should work'}],
+        ['this/should/work', {too: 'yes'}],
+      ]),
+    ],
+    [
+      'should accept function returning null',
+      ensurePlugins([
+        function plugin() {
+          return null;
+        },
+      ]),
+    ],
+    [
+      'should accept function returning plugin',
+      ensurePlugins([
+        function plugin() {
+          return {name: 'plugin'};
+        },
+      ]),
+    ],
+    [
+      'should accept function returning plugin or null',
+      ensurePlugins([
+        function plugin() {
+          return Math.random() > 0.5 ? null : {name: 'plugin'};
+        },
+      ]),
+    ],
+    [
+      'should accept async function returning null',
+      ensurePlugins([
+        async function plugin() {
+          return null;
+        },
+      ]),
+    ],
+    [
+      'should accept async function returning plugin',
+      ensurePlugins([
+        async function plugin() {
+          return {name: 'plugin'};
+        },
+      ]),
+    ],
+    [
+      'should accept function returning plugin or null',
+      ensurePlugins([
+        async function plugin() {
+          return Math.random() > 0.5 ? null : {name: 'plugin'};
+        },
+      ]),
+    ],
+    [
+      'should accept [function, object] for plugin',
+      [[() => {}, {it: 'should work'}]],
+    ],
+    [
+      'should accept false/null for plugin',
+      ensurePlugins([false as const, null, 'classic']),
+    ],
+  ])(`%s for the input of: %p`, (_message, plugins) => {
+    expect(() => {
+      normalizeConfig({
+        plugins,
+      } as Config);
+    }).not.toThrow();
+  });
+});
+
+describe('themes', () => {
+  it.each([
+    ['should throw error if themes is not array', {}],
+    [
+      "should throw error if themes is not a string and it's not an array #1",
+      [123],
+    ],
+    [
+      'should throw error if themes is not an array of [string, object][] #1',
+      [['example/path', 'wrong parameter here']],
+    ],
+    [
+      'should throw error if themes is not an array of [string, object][] #2',
+      [[{}, 'example/path']],
+    ],
+    [
+      'should throw error if themes is not an array of [string, object][] #3',
+      [[{}, {}]],
+    ],
+  ])(`%s for the input of: %p`, (_message, themes) => {
+    expect(() => {
+      normalizeConfig({
+        // @ts-expect-error: test
+        themes,
+      });
+    }).toThrowErrorMatchingSnapshot();
+  });
+
+  it.each([
+    ['should accept [string] for themes', ['plain/string']],
+    [
+      'should accept string[] for themes',
+      ['plain/string', 'another/plain/string/path'],
+    ],
+    [
+      'should accept [string, object] for themes',
+      [['plain/string', {it: 'should work'}]],
+    ],
+    [
+      'should accept [string, object][] for themes',
+      [
+        ['plain/string', {it: 'should work'}],
+        ['this/should/work', {too: 'yes'}],
+      ],
+    ],
+    [
+      'should accept ([string, object]|string)[] for themes',
+      [
+        'plain/string',
+        ['plain', {it: 'should work'}],
+        ['this/should/work', {too: 'yes'}],
+      ],
+    ],
+    ['should accept function for theme', [function theme() {}]],
+    [
+      'should accept [function, object] for theme',
+      [[function theme() {}, {it: 'should work'}]],
+    ],
+    ['should accept false/null for themes', [false, null, 'classic']],
+  ])(`%s for the input of: %p`, (_message, themes) => {
+    expect(() => {
+      normalizeConfig({
+        themes,
+      } as Config);
+    }).not.toThrow();
+  });
+
+  it('throws error if themes is not array', () => {
+    expect(() => {
+      normalizeConfig({
+        // @ts-expect-error: test
+        themes: {},
+      });
+    }).toThrowErrorMatchingInlineSnapshot(`
+      ""themes" must be an array
+      "
+    `);
+  });
+});
+
+describe('presets', () => {
+  it('throws error if presets is not array', () => {
+    expect(() => {
+      normalizeConfig({
+        // @ts-expect-error: test
+        presets: {},
+      });
+    }).toThrowErrorMatchingInlineSnapshot(`
+      ""presets" must be an array
+      "
+    `);
+  });
+
+  it('throws error if presets looks invalid', () => {
+    expect(() => {
+      normalizeConfig({
+        // @ts-expect-error: test
+        presets: [() => {}],
+      });
+    }).toThrowErrorMatchingInlineSnapshot(`
+      ""presets[0]" does not look like a valid preset config. A preset config entry should be one of:
+      - A tuple of [presetName, options], like \`["classic", { blog: false }]\`, or
+      - A simple string, like \`"classic"\`
+      "
+    `);
+  });
+
+  it('accepts presets as false / null', () => {
+    expect(() => {
+      normalizeConfig({
+        presets: [false, null, 'classic'],
+      });
+    }).not.toThrow();
+  });
+});
+
 describe('future', () => {
   it('accepts future - undefined', () => {
     expect(
@@ -737,6 +815,7 @@ describe('future', () => {
     });
 
     it('rejects router - null', () => {
+      // @ts-expect-error: bad value
       const router: DocusaurusConfig['future']['experimental_router'] = null;
       expect(() =>
         normalizeConfig({
@@ -976,6 +1055,7 @@ describe('future', () => {
       });
 
       it('rejects namespace - null', () => {
+        // @ts-expect-error: bad value
         const storage: Partial<StorageConfig> = {namespace: null};
         expect(() =>
           normalizeConfig({