add claude skills

skills/dbt-yaml-testing/SKILL.md

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+---
+name: dbt_yaml_testing
+description: "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**
+```yaml
+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).
+
+```yaml
+    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`:
+```yaml
+        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):
+```sql
+-- 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.