test_runner: add level parameter to reporter.diagnostic

Added a parameter to allow severity-based formatting for
diagnostic messages. Defaults to 'info'.
This update enables better control over message presentation
(e.g., coloring) based on severity levels such as 'info', 'warn',
and 'error'.

Refs: https://github.com/nodejs/node/issues/55922
PR-URL: https://github.com/nodejs/node/pull/57923
Reviewed-By: Pietro Marchini <pietro.marchini94@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

doc/api/test.md

@@ -3016,6 +3016,11 @@ defined. The corresponding declaration ordered event is `'test:start'`.
     `undefined` if the test was run through the REPL.
   * `message` {string} The diagnostic message.
   * `nesting` {number} The nesting level of the test.
+  * `level` {string} The severity level of the diagnostic message.
+    Possible values are:
+    * `'info'`: Informational messages.
+    * `'warn'`: Warnings.
+    * `'error'`: Errors.
 
 Emitted when [`context.diagnostic`][] is called.
 This event is guaranteed to be emitted in the same order as the tests are

lib/internal/test_runner/reporter/spec.js

@@ -94,8 +94,10 @@ class SpecReporter extends Transform {
       case 'test:stderr':
       case 'test:stdout':
         return data.message;
-      case 'test:diagnostic':
-        return `${reporterColorMap[type]}${indent(data.nesting)}${reporterUnicodeSymbolMap[type]}${data.message}${colors.white}\n`;
+      case 'test:diagnostic':{
+        const diagnosticColor = reporterColorMap[data.level] || reporterColorMap['test:diagnostic'];
+        return `${diagnosticColor}${indent(data.nesting)}${reporterUnicodeSymbolMap[type]}${data.message}${colors.white}\n`;
+      }
       case 'test:coverage':
         return getCoverageReport(indent(data.nesting), data.summary,
                                  reporterUnicodeSymbolMap['test:coverage'], colors.blue, true);

lib/internal/test_runner/reporter/utils.js

@@ -37,6 +37,15 @@ const reporterColorMap = {
   get 'test:diagnostic'() {
     return colors.blue;
   },
+  get 'info'() {
+    return colors.blue;
+  },
+  get 'warn'() {
+    return colors.yellow;
+  },
+  get 'error'() {
+    return colors.red;
+  },
 };
 
 function indent(nesting) {

lib/internal/test_runner/test.js

@@ -1235,7 +1235,7 @@ class Test extends AsyncResource {
           if (actual < threshold) {
             harness.success = false;
             process.exitCode = kGenericUserError;
-            reporter.diagnostic(nesting, loc, `Error: ${NumberPrototypeToFixed(actual, 2)}% ${name} coverage does not meet threshold of ${threshold}%.`);
+            reporter.diagnostic(nesting, loc, `Error: ${NumberPrototypeToFixed(actual, 2)}% ${name} coverage does not meet threshold of ${threshold}%.`, 'error');
           }
         }
 

lib/internal/test_runner/tests_stream.js

@@ -116,11 +116,12 @@ class TestsStream extends Readable {
     });
   }
 
-  diagnostic(nesting, loc, message) {
+  diagnostic(nesting, loc, message, level = 'info') {
     this[kEmitMessage]('test:diagnostic', {
       __proto__: null,
       nesting,
       message,
+      level,
       ...loc,
     });
   }

test/parallel/test-runner-coverage-thresholds.js

@@ -90,6 +90,26 @@ for (const coverage of coverages) {
     assert(!findCoverageFileForPid(result.pid));
   });
 
+  test(`test failing ${coverage.flag} with red color`, () => {
+    const result = spawnSync(process.execPath, [
+      '--test',
+      '--experimental-test-coverage',
+      '--test-coverage-exclude=!test/**',
+      `${coverage.flag}=99`,
+      '--test-reporter', 'spec',
+      fixture,
+    ], {
+      env: { ...process.env, FORCE_COLOR: '3' },
+    });
+
+    const stdout = result.stdout.toString();
+    // eslint-disable-next-line no-control-regex
+    const redColorRegex = /\u001b\[31mℹ Error: \d{2}\.\d{2}% \w+ coverage does not meet threshold of 99%/;
+    assert.match(stdout, redColorRegex, 'Expected red color code not found in diagnostic message');
+    assert.strictEqual(result.status, 1);
+    assert(!findCoverageFileForPid(result.pid));
+  });
+
   test(`test failing ${coverage.flag}`, () => {
     const result = spawnSync(process.execPath, [
       '--test',

test/parallel/test-runner-run.mjs

@@ -33,6 +33,24 @@ describe('require(\'node:test\').run', { concurrency: true }, () => {
     for await (const _ of stream);
   });
 
+  it('should emit diagnostic events with level parameter', async () => {
+    const diagnosticEvents = [];
+
+    const stream = run({
+      files: [join(testFixtures, 'coverage.js')],
+      reporter: 'spec',
+    });
+
+    stream.on('test:diagnostic', (event) => {
+      diagnosticEvents.push(event);
+    });
+    // eslint-disable-next-line no-unused-vars
+    for await (const _ of stream);
+    assert(diagnosticEvents.length > 0, 'No diagnostic events were emitted');
+    const infoEvent = diagnosticEvents.find((e) => e.level === 'info');
+    assert(infoEvent, 'No diagnostic events with level "info" were emitted');
+  });
+
   const argPrintingFile = join(testFixtures, 'print-arguments.js');
   it('should allow custom arguments via execArgv', async () => {
     const result = await run({ files: [argPrintingFile], execArgv: ['-p', '"Printed"'] }).compose(spec).toArray();