How values are generated

Generators aim at each keyword, then a validator checks the result. How a keyword is handled decides how fast generation is, never whether a value is valid.

Keywords	Handling
type, enum, const, numeric bounds, multipleOf, minLength, maxLength, minItems, maxItems, uniqueItems, items, prefixItems, contains, minContains, properties, required, additionalProperties, patternProperties, propertyNames, minProperties, dependentRequired, dependentSchemas	Generated directly.
pattern	Generated from the regular expression. Several combine when they can (startsWith(), contains(), endsWith()). Lookaround is removed first, since fast-check can't generate from it.
format	Generated for every format Juniper knows by name. Any other is a plain string.
allOf, anyOf, $ref, recursion	Resolved, then generated directly. anyOf reaches every branch.
oneOf, if/then/else	Each branch is generated, and values matching too many are dropped.
not, unevaluatedItems, unevaluatedProperties, maxContains, maxProperties	Values that don't match are dropped.

Deliberate limits

• Objects get a few undeclared properties unless additionalProperties says otherwise, since a real payload can have them.
• Recursion stops a few levels deep, as each level multiplies the size of a value.
• Numbers mix doubles with integers, since doubles alone are nearly all huge or tiny.
• A schema with a great many conditionals only reaches its first 64 combinations.

When generation gives up

A value is rejected up to 1000 times in a row before generation throws UnsatisfiableSchemaError. That only happens for a schema random values rarely satisfy, such as a backreference in a pattern. Use a simpler schema, or a hand-written arbitrary with .chain(), for that part.