As described in delivery methodology, we decompose the project into big parts, then medium ones and eventually small. We track quality by verifying and validating delivery on every level of delivery. From individual tasks, to modules and components.
How to make sure that high-level business goals reached? We set business-level acceptance criteria together with the key stakeholders and make sure that further planning and delivery on component level would satisfy these.
Once the project is decomposed into components each of them gets acceptance criteria to verify and validate it once delivered.
Further, once components are decomposed into modules each of them also gets acceptance criteria to be verified and valudated once ready.
Afterwards, user stories get their own acceptance criterias and coding tasks get test cases to be passed to be ready for review.
And once delivery starts - the journey goes back up to the big project goals. First granular tasks are run versus created test cases, then they get assembled into a module that is checked against its acceptance criteria on module-level, and then the same happens wirh components and an entire project goals!