Objects¶
{"type": "object"} generates a random dict. Without any property schemas, keys are generated from the default_property_schema (default: a username-style string) and values are random JSON-compatible types.
Declared properties¶
properties / required¶
{
"type": "object",
"properties": {
"name": {"type": "string"},
"age": {"type": "integer", "minimum": 0, "maximum": 120},
"email": {"type": "string", "format": "email"}
},
"required": ["name", "age"]
}
Strategy: all required properties are always generated. Non-required properties are included randomly (50 % chance each by default). Each property value is generated from its own sub-schema.
Additional properties¶
additionalProperties¶
Accepts a boolean or a sub-schema.
Boolean false — no extra properties:
{
"type": "object",
"properties": {"x": {"type": "number"}, "y": {"type": "number"}},
"additionalProperties": false,
"required": ["x", "y"]
}
Schema — extra properties follow a type:
{
"type": "object",
"properties": {"id": {"type": "integer"}},
"additionalProperties": {"type": "boolean"},
"minProperties": 3,
"maxProperties": 4
}
Strategy: declared properties are generated first. If more properties are needed to reach minProperties, additional ones are generated using the additionalProperties schema (or any type if it is true). Property names for additional properties come from the default_property_schema context option. When unevaluatedProperties is also present, keys produced through an additionalProperties schema are treated as already evaluated.
Limitations: additionalProperties: false with minProperties greater than the number of declared properties raises UnsatisfiableConstraintsError. If additionalProperties is just true, those extra keys are still considered unevaluated for unevaluatedProperties processing because there is no schema application to mark them as evaluated.
Pattern properties¶
patternProperties¶
{
"type": "object",
"patternProperties": {"^x-": {"type": "string"}},
"minProperties": 2,
"maxProperties": 3
}
Strategy: for each pattern key, generates one property whose name matches the pattern and whose value conforms to the schema. If propertyNames is present, the generated key must satisfy both the pattern and the propertyNames sub-schema before it is accepted. Additional properties (not covered by any pattern) may also be generated to satisfy minProperties.
Limitations: generated keys are not guaranteed to be human-readable; the pattern engine may produce Unicode characters or unusual strings when the regex allows them. If patternProperties and propertyNames together leave no valid key space, generation raises UnsatisfiableConstraintsError.
Property name schema¶
propertyNames¶
{
"type": "object",
"propertyNames": {"pattern": "^[a-z]{3,8}$"},
"additionalProperties": {"type": "integer"},
"minProperties": 2,
"maxProperties": 3
}
Strategy: property names are generated by applying propertyNames as a string sub-schema (using the pattern strategy). The same constraint also applies when keys are generated for patternProperties and schema-valued additionalProperties.
Limitations: propertyNames applies to all property names including those declared in properties. If a declared property name does not conform to propertyNames, or if propertyNames conflicts with patternProperties, the schema is inconsistent and generation may raise UnsatisfiableConstraintsError.
Unevaluated properties¶
unevaluatedProperties¶
{
"type": "object",
"properties": {"name": {"type": "string"}},
"required": ["name"],
"additionalProperties": {"type": "integer"},
"unevaluatedProperties": false,
"minProperties": 2,
"maxProperties": 2
}
Strategy: after generating declared, patterned, and additional properties, the generator computes which keys have been evaluated by the active object keywords. Keys produced by schema-valued additionalProperties are preserved as evaluated keys; remaining unevaluated keys are either removed (false) or regenerated from the unevaluatedProperties schema.
Limitations: only keys touched by a schema-valued additionalProperties are treated as evaluated through that keyword. When additionalProperties is true, extra keys remain unevaluated and may therefore be removed or rewritten by unevaluatedProperties.
Property count¶
minProperties / maxProperties¶
{
"type": "object",
"additionalProperties": {"type": "boolean"},
"minProperties": 2,
"maxProperties": 3
}
Strategy: the total property count is chosen uniformly in [minProperties, maxProperties].
Dependent keywords¶
dependentRequired¶
{
"type": "object",
"properties": {
"credit_card": {"type": "string"},
"billing_address": {"type": "string"},
"name": {"type": "string"}
},
"required": ["name"],
"dependentRequired": {"credit_card": ["billing_address"]}
}
{
"name": "Unit study thus executive cost do.",
"billing_address": "Purpose top nice case agree.",
"credit_card": "Property administration news term meeting who style.",
}
Strategy: if a trigger property is present in the generated object, all properties it depends on are added automatically. The trigger property itself may or may not appear (it is not required unless listed there).
dependentSchemas¶
{
"type": "object",
"properties": {"plan": {"type": "string", "enum": ["free", "pro"]}},
"required": ["plan"],
"dependentSchemas": {
"plan": {"properties": {"seats": {"type": "integer", "minimum": 1}}}
}
}
Strategy: if a trigger property ends up in the object, the dependent schema is merged into the overall object schema and generation continues with the merged constraints. This means additional properties or constraints from the dependent schema are applied.
Limitations: dependentSchemas merging uses the same constraint-merge logic as allOf. Conflicting types between the base schema and a dependent schema will raise UnsatisfiableConstraintsError.