test: change promise to async/await in debugger-watcher

PR-URL: #44687
Reviewed-By: Franziska Hinkelmann <franziska.hinkelmann@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>

test/sequential/test-debugger-watchers.mjs

@@ -0,0 +1,49 @@
+import { skipIfInspectorDisabled } from '../common/index.mjs';
+skipIfInspectorDisabled();
+
+import { path } from '../common/fixtures.mjs';
+import startCLI from '../common/debugger.js';
+
+import assert from 'assert';
+
+const script = path('debugger', 'break.js');
+const cli = startCLI([script]);
+
+function onFatal(error) {
+  cli.quit();
+  throw error;
+}
+
+// Stepping through breakpoints.
+try {
+  await cli.waitForInitialBreak();
+  await cli.waitForPrompt();
+  await cli.command('watch("x")');
+  await cli.command('watch("\\"Hello\\"")');
+  await cli.command('watch("42")');
+  await cli.command('watch("NaN")');
+  await cli.command('watch("true")');
+  await cli.command('watch("[1, 2]")');
+  await cli.command('watch("process.env")');
+  await cli.command('watchers');
+
+  assert.match(cli.output, /x is not defined/);
+
+  await cli.command('unwatch("42")');
+  await cli.stepCommand('n');
+
+  assert.match(cli.output, /0: x = 10/);
+  assert.match(cli.output, /1: "Hello" = 'Hello'/);
+  assert.match(cli.output, /2: NaN = NaN/);
+  assert.match(cli.output, /3: true = true/);
+  assert.match(cli.output, /4: \[1, 2\] = \[ 1, 2 \]/);
+  assert.match(
+    cli.output,
+    /5: process\.env =\n\s+\{[\s\S]+,\n\s+\.\.\. \}/,
+    'shows "..." for process.env'
+  );
+
+  await cli.quit();
+} catch (error) {
+  onFatal(error);
+}