When I change my dependencies from pulumi-aws 3.17.0 to 3.18.0 (no other changes), I get two errors when running my tests. First:

error TS2339: Property 'promise' does not exist on type 'Output<string>'.

66           resource.arn.promise()

My test file includes this:

declare module '@pulumi/pulumi' {
  export interface OutputInstance<T> {
    promise(withUnknowns?: boolean): Promise<T>;
  }
}

This has worked until 3.17.0, and in theory has nothing to do with pulumi-aws...