test: add test for using --print with promises

test/parallel/test-cli-print-promise.mjs

@@ -0,0 +1,93 @@
+import { spawnPromisified } from '../common/index.mjs';
+import assert from 'node:assert';
+import { execPath } from 'node:process';
+import { describe, it } from 'node:test';
+
+
+describe('--print with a promise', { concurrency: true }, () => {
+  it('should handle directly-fulfilled promises', async () => {
+    const result = await spawnPromisified(execPath, [
+      '--print',
+      'Promise.resolve(42)',
+    ]);
+
+    assert.deepStrictEqual(result, {
+      code: 0,
+      signal: null,
+      stderr: '',
+      stdout: 'Promise { 42 }\n',
+    });
+  });
+
+  it('should handle promises fulfilled after one tick', async () => {
+    const result = await spawnPromisified(execPath, [
+      '--print',
+      'Promise.resolve().then(()=>42)',
+    ]);
+
+    assert.deepStrictEqual(result, {
+      code: 0,
+      signal: null,
+      stderr: '',
+      stdout: 'Promise { <pending> }\n',
+    });
+  });
+
+  it('should handle promise that never settles', async () => {
+    const result = await spawnPromisified(execPath, [
+      '--print',
+      'new Promise(()=>{})',
+    ]);
+
+    assert.deepStrictEqual(result, {
+      code: 0,
+      signal: null,
+      stderr: '',
+      stdout: 'Promise { <pending> }\n',
+    });
+  });
+
+  it('should output something if process exits before promise settles', async () => {
+    const result = await spawnPromisified(execPath, [
+      '--print',
+      'setTimeout(process.exit,100, 0);timers.promises.setTimeout(200)',
+    ]);
+
+    assert.deepStrictEqual(result, {
+      code: 0,
+      signal: null,
+      stderr: '',
+      stdout: 'Promise { <pending> }\n',
+    });
+  });
+
+  it('should handle rejected promises', async () => {
+    const result = await spawnPromisified(execPath, [
+      '--unhandled-rejections=none',
+      '--print',
+      'Promise.reject(1)',
+    ]);
+
+    assert.deepStrictEqual(result, {
+      code: 0,
+      signal: null,
+      stderr: '',
+      stdout: 'Promise { <rejected> 1 }\n',
+    });
+  });
+
+  it('should handle promises that reject after one tick', async () => {
+    const result = await spawnPromisified(execPath, [
+      '--unhandled-rejections=none',
+      '--print',
+      'Promise.resolve().then(()=>Promise.reject(1))',
+    ]);
+
+    assert.deepStrictEqual(result, {
+      code: 0,
+      signal: null,
+      stderr: '',
+      stdout: 'Promise { <pending> }\n',
+    });
+  });
+});