test_runner: fix infinite loop when files are undefined in test runner

PR-URL: nodejs#51047
Fixes: nodejs#48823
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: Moshe Atlow <moshe@atlow.co.il>
Reviewed-By: James M Snell <jasnell@gmail.com>

lib/internal/test_runner/runner.js

@@ -487,6 +487,9 @@ function run(options = kEmptyObject) {
   }
 
   const root = createTestTree({ __proto__: null, concurrency, timeout, signal });
+  if (process.env.NODE_TEST_CONTEXT !== undefined) {
+    return root.reporter;
+  }
   let testFiles = files ?? createTestFileList();
 
   if (shard) {

test/parallel/test-runner-run.mjs

@@ -466,4 +466,37 @@ describe('require(\'node:test\').run', { concurrency: true }, () => {
         }));
     });
   });
+
+  it('should run with no files', async () => {
+    const stream = run({
+      files: undefined
+    }).compose(tap);
+    stream.on('test:fail', common.mustNotCall());
+    stream.on('test:pass', common.mustNotCall());
+
+    // eslint-disable-next-line no-unused-vars
+    for await (const _ of stream);
+  });
+
+  it('should run with no files and use spec reporter', async () => {
+    const stream = run({
+      files: undefined
+    }).compose(spec);
+    stream.on('test:fail', common.mustNotCall());
+    stream.on('test:pass', common.mustNotCall());
+
+    // eslint-disable-next-line no-unused-vars
+    for await (const _ of stream);
+  });
+
+  it('should run with no files and use dot reporter', async () => {
+    const stream = run({
+      files: undefined
+    }).compose(dot);
+    stream.on('test:fail', common.mustNotCall());
+    stream.on('test:pass', common.mustNotCall());
+
+    // eslint-disable-next-line no-unused-vars
+    for await (const _ of stream);
+  });
 });