Contributing to Schemas

Schema Docs

Schema Documentation are hosted on branch gh-pages which is hosted via GitHub Pages at

There is an automated workflow jsonschema2md which publishes schemas, documentation and examples. If you want to edit top-level page please send a pull-request to gh-pages branch.

Adding a new schema

If you want to add a new schema to buildtest you need to do the following:

  1. Add schema file in buildtest/schemas and schema file must end in .schema.json. If it’s a sub-schema it must in format <name>-<version>.schema.json. For example a schema name script-v2.0.schema.json will be sub-schema script and version 2.0.

  2. Their should be a folder that corresponds to name of schema in examples directory.

  3. There should be a list of invalid and valid examples for schema.

  4. There should be regression testfile in schema_tests to test the schema.

Be sure to update properties and take account for:

  • a property being required or not

  • Make use of additionalProperties: false when defining properties so that additional keys in properties are not passed in.

  • requirements for the values provided (types, lengths, etc.)

  • If you need help, see JSON Schema Resources or reach out to someone in Slack.

Running Schema Tests

The schema tests are found in folder tests/schema_tests which has regression test for each schema. The purpose for schema test is to ensure Buildspecs are written according to specification outlined in schemas. Furthermore, we have edge cases to test invalid Buildspec recipes to ensure schemas are working as expected.

To run all schema test you can run via marker:

pytest -v -m schema

JSON Definitions

We store all JSON definitions in defintions.schema.json which are fields need to be reused in other schemas. A JSON definition is defined under defintions field, in this example we define a definition anchor list_of_strings that declares an array of string:

  "definitions": {
    "list_of_strings": {
      "type": "array",
      "uniqueItems": true,
      "minItems": 1,
      "items": {"type": "string"}

A definition anchor can be referenced using $ref keyword. In example below we declare a definitions string_or_list that uses $ref that points to anchor list_of_strings:

"string_or_list": {
  "oneOf": [
    {"type": "string"},
    {"$ref": "#/definitions/list_of_strings"}

For example the tags field is defined in definitions.schema.json that references definition string_or_list:

"tags": {
  "description": "Classify tests using a tag name, this can be used for categorizing test and building tests using ``--tags`` option",
  "$ref": "#/definitions/string_or_list"

The tags field is used in other schemas like compiler.schema.json and script.schema.json. In this example we declare tags field and reference tags anchor from definitions.schema.json:

"tags": {
  "$ref": "definitions.schema.json#/definitions/tags"

It’s worth noting each schema must have a $id in order for JSON to resolve references ($ref). For example the definitions schema has the following id:

"$id": "definitions.schema.json"

It’s recommended each schema has a $schema, $title, description field for each schema. Currently, we support JSON Schema Draft7 so our schema field must be set to the following:

"$schema": "",

JSON Schema Resources

The following sites (along with the files here) can be useful to help with your development of a schema.

If you have issues with writing json schema please join the JSON-SCHEMA Slack Channel