An important part of testing and assessment is the feedback that a second-language educator offers students to correct errors. While the optimal mode and delivery of feedback remain a question of some debate, important research (see Lourdes Ortega’s Second Language Acquisition, for example) suggest that providing feedback which engages students in correcting themselves and thus developing a mechanism for self-regulation is the most productive. Indeed, students who correct their own mistakes – whether guided or not to this correction by an educator – will better internalize and assimilate the rules of grammar / syntax / vocabulary that they previously mistook.
This dialogical type of feedback process – by which learner and educator co-produce and negotiate feedback – can assume multiple forms depending on the assessment in question. For writing assignments, for example, best practices dictate the use of multiple drafts, which allow educators to signal errors with the use of a correction code (for instance, a word may be circled with “conj.” for “conjugation” written above it, meaning that a student should doublecheck that the conjugation is correct). Student thus have the opportunity to identify and correct their own errors, which changes their role in the feedback process from passive to active.
As another example – this time gleaned from The Cambridge Handbook of Corrective Feedback in Second Language Learning and Teaching – corrective feedback during meaning-focused conversations offers another fertile ground for involving learners in the process of identifying and correcting errors. Over the course of a conversation, when learners fail to understand an interlocutor’s meaning or to communicate their ideas, the fluent interlocutor can seize the occasion to ask for clarification and employ circumlocution in order to show the learner how to seek out clarification, reformulate, and negotiate meaning.
Whatever the case may be, feedback should constitute an important and active step in the process of language learning. This page links to resources that talk about research into feedback in second language acquisition, in addition to resources that provide examples and practical advice for optimizing one's feedback as a language educator.
Illustration cited from : Kerr, P. (2020). Giving feedback to language learners. Part of the Cambridge papers in ELT series. [pdf] Cambridge: Cambridge University Press
The Cambridge Handbook of Corrective Feedback in Second Language Learning and Teaching by 
Written Corrective Feedback in Second Language Acquisition and Writing by 
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