test_runner: display dot report as wide as the terminal width

lib/internal/test_runner/reporter/dot.js

@@ -1,17 +1,27 @@
 'use strict';
+const { MathMax } = primordials;
 
 module.exports = async function* dot(source) {
   let count = 0;
+  let columns = getLineLength();
   for await (const { type } of source) {
     if (type === 'test:pass') {
       yield '.';
     }
     if (type === 'test:fail') {
       yield 'X';
     }
-    if ((type === 'test:fail' || type === 'test:pass') && ++count % 20 === 0) {
+    if ((type === 'test:fail' || type === 'test:pass') && ++count === columns) {
       yield '\n';
+
+      // Getting again in case the terminal was resized.
+      columns = getLineLength();
+      count = 0;
     }
   }
   yield '\n';
 };
+
+function getLineLength() {
+  return MathMax(process.stdout.columns ?? 20, 20);
+}

test/fixtures/test-runner/output/dot_output_custom_columns.js

@@ -0,0 +1,18 @@
+// Flags: --test-reporter=dot
+'use strict';
+process.stdout.columns = 30;
+
+const test = require('node:test');
+const { setTimeout } = require('timers/promises');
+
+for (let i = 0; i < 100; i++) {
+  test(i + ' example', async () => {
+    if (i === 0) {
+      // So the reporter will run before all tests has started
+      await setTimeout(10);
+    }
+    // resize
+    if (i === 28)
+      process.stdout.columns = 41;
+  });
+}

test/fixtures/test-runner/output/dot_output_custom_columns.snapshot

@@ -0,0 +1,3 @@
+..............................
+.........................................
+.............................

test/parallel/test-runner-output.mjs

@@ -46,6 +46,7 @@ const tests = [
   { name: 'test-runner/output/unresolved_promise.js' },
   { name: 'test-runner/output/default_output.js', transform: specTransform, tty: true },
   { name: 'test-runner/output/arbitrary-output.js' },
+  { name: 'test-runner/output/dot_output_custom_columns.js', transform: specTransform, tty: true },
 ].map(({ name, tty, transform }) => ({
   name,
   fn: common.mustCall(async () => {