tests:
  - input_series:
      - series: 'join_1{a="1",b="2"}'
        values: 1
      - series: 'join_2{a="1",b="3"}'
        values: 2
      - series: 'join_2{a="1",b="4"}'
        values: 3

    promql_expr_test:
      # This PromQL generates an error.
      - expr: "join_1 + on(a) join_2"
