mockId function
Returns an incrementing integer ID starting from 0.
Each call to the returned function produces the next integer as a string.
Mirrors mockId from the JS AI SDK v6 ai/test sub-path.
final id = mockId();
expect(id(), '0');
expect(id(), '1');
Implementation
String Function() mockId() {
var counter = 0;
return () => '${counter++}';
}