My schema is:

const scenerioSchema = Joi.object({
  drawingNode: Joi.object({
    moduleRackOutputs: Joi.array()
      .items(
        Joi.object({
          moduleId: Joi.string().required()
        })
      )
      .unique((a, b) => a.moduleId !== b.moduleId)
  })
})

My data is:

const mockScenario1 = {
  drawingNode: {
    moduleRackOutputs: [
      {
        moduleId: 'module1'
      },
      {
        moduleId: 'module2'
      }
    ]
  }
}

When I validate with:

const validationResponse = scenerioSchema.validate(mockScenario1)

I get:

{
      validationResponse: {
        value: { drawingNode: [Object] },
        error: [Error [ValidationError]: "drawingNode.moduleRackOutputs[1]" contains a duplicate value] {
          _original: [Object],
          details: [Array]
        }
      }
    }

But (a) that's not true - the items are not duplicates and (b) I want an error to occur if the moduleId is different.

What am I doing wrong?