Custom Generators

SqlProof maps PostgreSQL types to fast-check arbitraries automatically. For tighter control — realistic emails, specific numeric ranges, domain-constrained strings — override them via proof.customize().

Basic Override

import fc from 'fast-check';

proof.customize('products', {
  price: fc.float({ min: 0.01, max: 9999.99, noNaN: true }),
  name: fc.string({ minLength: 1, maxLength: 100 }),
});

Common Patterns

Numeric ranges

proof.customize('products', {
  price: fc.float({ min: 0.01, max: 9999.99, noNaN: true }),
  stock: fc.integer({ min: 0, max: 10000 }),
  discount_pct: fc.float({ min: 0, max: 0.5, noNaN: true }),
});

Constrained strings

proof.customize('customers', {
  email: fc.emailAddress(),
  name: fc.string({ minLength: 2, maxLength: 100 }),
});

Picking from a fixed set

proof.customize('orders', {
  currency: fc.constantFrom('USD', 'EUR', 'GBP'),
  region: fc.constantFrom('us-east', 'us-west', 'eu-central'),
});

Dates in a specific range

proof.customize('orders', {
  created_at: fc.date({
    min: new Date('2020-01-01'),
    max: new Date('2024-12-31'),
    noInvalidDate: true,
  }),
});

Default Type Mappings

PostgreSQL Type	Default Arbitrary
integer, int4	fc.integer({ min: -2147483648, max: 2147483647 })
bigint	fc.bigInt()
smallint	fc.integer({ min: -32768, max: 32767 })
numeric(p,s), decimal	fc.float() scaled to precision
real, float4	fc.float({ noNaN: true, noDefaultInfinity: true })
double precision	fc.double({ noNaN: true, noDefaultInfinity: true })
boolean	fc.boolean()
text	fc.string({ unit: 'grapheme', maxLength: 255 })
varchar(n)	fc.string({ unit: 'grapheme', maxLength: n })
uuid	fc.uuid()
timestamp, timestamptz	fc.date({ noInvalidDate: true }) clamped to 1970–2099
date	fc.date() formatted as YYYY-MM-DD
json, jsonb	fc.jsonValue()
enum types	fc.constantFrom(...enumValues)
integer[], etc.	fc.array() of base type