How can i use ref to another models besides from User?

i want to use ref to ex: Job models, but its give some error say: job: path "job" is required.
here's my code:

`tes: {
type: Schema.ObjectId,
ref: 'Job',
required: true
},`

The issue names no repository files or tests and provides only a schema snippet. Start by locating the model-reference handling and reproducing the reported "job: path \"job\" is required" error; done would require a documented or tested resolution for references to Job models.

Written by the indexing model from the issue text.