You define a new generic test on model customers in a YAML file:version: 2models:- name:...

This error occurs because the YAML structure is incorrectly indented, causing dbt’s parser (and YAML itself) to misinterpret the test definitions. In dbt, generic tests must be declared as a list under the tests: key, but YAML is extremely sensitive to indentation levels. In the faulty YAML, unique and not_null are indented incorrectly relative to the tests: key, which produces the error: “mapping values are not allowed in this context.”

According to the dbt Testing documentation, valid generic test syntax follows this exact pattern:

columns:

- name: id

tests:

- unique

- not_null

The indentation under tests: must be consistent and aligned so that YAML interprets the items as list elements, not as malformed mappings. When indentation is wrong, YAML attempts to parse list entries as key-value mappings, which leads to the error seen during compilation.

dbt does not require generic test names to be quoted, nor does it expect tests to be a dictionary. The test list format is correct—only the indentation is wrong. Therefore, the root cause is incorrect YAML indentation, making Option D correct.