fix: respect runInBand being passed in watch mode

CHANGELOG.md

@@ -17,6 +17,7 @@
 - `[babel-plugin-jest-hoist]` Use `denylist` instead of the deprecated `blacklist` for Babel 8 support ([#14109](https://github.com/jestjs/jest/pull/14109))
 - `[expect]` Check error instance type for `toThrow/toThrowError` ([#14576](https://github.com/jestjs/jest/pull/14576))
 - `[jest-circus]` [**BREAKING**] Prevent false test failures caused by promise rejections handled asynchronously ([#14315](https://github.com/jestjs/jest/pull/14315))
+- `[jest-config]` Make sure to respect `runInBand` option ([#14578](https://github.com/facebook/jest/pull/14578))
 - `[@jest/expect-utils]` Fix comparison of `DataView` ([#14408](https://github.com/jestjs/jest/pull/14408))
 - `[jest-leak-detector]` Make leak-detector more aggressive when running GC ([#14526](https://github.com/jestjs/jest/pull/14526))
 - `[jest-util]` Make sure `isInteractive` works in a browser ([#14552](https://github.com/jestjs/jest/pull/14552))

e2e/__tests__/__snapshots__/showConfig.test.ts.snap

@@ -130,6 +130,7 @@ exports[`--showConfig outputs config info and exits 1`] = `
     "passWithNoTests": false,
     "projects": [],
     "rootDir": "<<REPLACED_ROOT_DIR>>",
+    "runInBand": false,
     "runTestsByPath": false,
     "seed": <<RANDOM_SEED>>,
     "skipFilter": false,

packages/jest-config/src/__tests__/normalize.test.ts

@@ -2215,3 +2215,17 @@ describe('randomize', () => {
     expect(options.randomize).toBeFalsy();
   });
 });
+
+describe('runInBand', () => {
+  test('always set it', async () => {
+    const {options} = await normalize({rootDir: '/root/'}, {} as Config.Argv);
+    expect(options.runInBand).toBe(false);
+  });
+
+  test('respect argv', async () => {
+    const {options} = await normalize({rootDir: '/root/'}, {
+      runInBand: true,
+    } as Config.Argv);
+    expect(options.runInBand).toBe(true);
+  });
+});

packages/jest-config/src/normalize.ts

@@ -1092,6 +1092,7 @@ export default async function normalize(
     10,
   );
   newOptions.maxWorkers = getMaxWorkers(argv, options);
+  newOptions.runInBand = argv.runInBand || false;
 
   if (newOptions.testRegex.length > 0 && options.testMatch) {
     throw createConfigError(