workspace/skills/dbt-yaml-testing/SKILL.md

name, description

name	description
dbt_yaml_testing	Step-by-step instructions for writing dbt schema.yml files with model descriptions, column descriptions, and data tests. Use for any dbt project.

Write dbt Schema YAML & Data Tests

Every dbt model needs a schema entry with descriptions and tests. This skill covers writing schema.yml files correctly.

---

Steps

1. Locate or create the schema file

• Naming convention: schema.yml (one per folder is fine) or <model_name>.yml.
• Place it in the same directory as the model.
• Source definitions use src_<system>.yml.

2. Add the model block

models:
  - name: <model_name>
    description: "One sentence: what this model represents, grain, and any key filters."

3. Add column definitions

• Every column should have a description:.
• Use data_tests: (not the deprecated tests: key).

    columns:
      - name: <primary_key_column>
        description: "Unique identifier for each row."
        data_tests:
          - unique
          - not_null

      - name: <foreign_key_column>
        description: "Foreign key to <other_model>."
        data_tests:
          - not_null
          - relationships:
              to: ref('<other_model>')
              field: <field_name>

      - name: <status_column>
        description: "Status of the record."
        data_tests:
          - accepted_values:
              values: ['active', 'inactive', 'pending']

4. Set test severity (optional override)

• Project default is usually warn. Override critical tests to error:

        data_tests:
          - unique:
              severity: error
          - not_null:
              severity: error

5. Add singular tests for complex assertions

• Place in tests/ directory.
• A passing test returns zero rows (the query selects failing records):

-- tests/assert_<model>_<condition>.sql
select <key_column>
from {{ ref('<model_name>') }}
where <failing_condition>

---

Minimum Required Tests Per Layer

Layer	Required Tests
Staging	unique + not_null on primary key
Transform	unique + not_null on unique_key columns
Marts (fact)	unique + not_null on PK; relationships on FK
Marts (dim)	unique + not_null on natural/surrogate key

---

YAML Style Rules

• 2-space indentation (no tabs).
• Use data_tests: not tests:.
• Every model must have a description:.
• Quote descriptions with "double quotes".

---

Template

See schema_template.yml in this folder.