Ensure verbose mode prints output synchronously

Fixes jestjs#8208

packages/jest-reporters/package.json

@@ -14,6 +14,7 @@
     "@jest/test-result": "^27.0.0-next.1",
     "@jest/transform": "^27.0.0-next.2",
     "@jest/types": "^27.0.0-next.1",
+    "@types/node": "*",
     "chalk": "^4.0.0",
     "collect-v8-coverage": "^1.0.0",
     "exit": "^0.1.2",

packages/jest-reporters/src/DefaultReporter.ts

@@ -43,15 +43,15 @@ export default class DefaultReporter extends BaseReporter {
     this._err = process.stderr.write.bind(process.stderr);
     this._status = new Status();
     this._bufferedOutput = new Set();
-    this._wrapStdio(process.stdout);
-    this._wrapStdio(process.stderr);
+    this.__wrapStdio(process.stdout);
+    this.__wrapStdio(process.stderr);
     this._status.onChange(() => {
       this._clearStatus();
       this._printStatus();
     });
   }
 
-  private _wrapStdio(stream: NodeJS.WritableStream | NodeJS.WriteStream) {
+  protected __wrapStdio(stream: NodeJS.WritableStream | NodeJS.WriteStream) {
     const originalWrite = stream.write;
 
     let buffer: Array<string> = [];

packages/jest-reporters/src/VerboseReporter.ts

@@ -29,6 +29,11 @@ export default class VerboseReporter extends DefaultReporter {
     this._globalConfig = globalConfig;
   }
 
+  // Verbose mode is for debugging. Buffering of output is undesirable.
+  // See https://github.com/facebook/jest/issues/8208
+  protected __wrapStdio() {
+  }
+
   static filterTestResults(
     testResults: Array<AssertionResult>,
   ): Array<AssertionResult> {

yarn.lock

@@ -1990,6 +1990,7 @@ __metadata:
     "@types/istanbul-lib-report": ^3.0.0
     "@types/istanbul-lib-source-maps": ^4.0.0
     "@types/istanbul-reports": ^3.0.0
+    "@types/node": "*"
     "@types/node-notifier": ^8.0.0
     chalk: ^4.0.0
     collect-v8-coverage: ^1.0.0