tuple index out of range in custom schema tests with select *

[abronner]

if a custom schema test returns the result of select * instead of select count(*), and the query returns 0 records, then the test fails with the error message: tuple index out of range.

schema tests should return a single row with a single column that contains the count of failures. if select * returns 0 records, dbt hits tuple index out of range when it tries to grab the first column in the first row of that result set.

to reproduce, add the following test to your model:

{% macro test_my_custom_schema_test(model, column_name) %}

SELECT * from {{ model }} WHERE 1=0

{% endmacro %}

result of dbt test:

Completed with 1 errors:

tuple index out of range

please add a better error message when a test returns a different result than what is expected.

[drewbanin]

Thanks @abronner! Agreed, a better error message here would be a great addition.

I just put a good first issue label on this issue - please let me know if it's something you'd be interested in contributing a fix for! I think the patch should be pretty self-contained :)

Thanks!