TableCustomization

TableCustomization is passed to proof.customize(table, overrides).

interface TableCustomization {
  fkDistribution?: Record<string, FkDistributionStrategy>;
  [columnName: string]: fc.Arbitrary<unknown> | Record<string, FkDistributionStrategy> | undefined;
}

type FkDistributionStrategy = 'zipf' | 'uniform' | 'adversarial';

Custom Column Generators

Override the default generator for any column with a fast-check arbitrary:

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 }),
  sku: fc.stringMatching(/^[A-Z]{2}-\d{4}$/),
});

FK Distribution Strategies

Control how foreign key values are assigned when referencing parent rows:

proof.customize('orders', {
  fkDistribution: { customer_id: 'zipf' },
});

Strategy	Behavior	Best for
uniform (default)	Equal probability per parent	General coverage
zipf	First parents get many children; later ones few	Realistic skewed data
adversarial	Only picks first, middle, and last parent	Boundary stress testing

Fluent Chaining

customize() returns this, enabling chaining:

proof
  .customize('products', { price: fc.float({ min: 0.01, max: 9999.99, noNaN: true }) })
  .customize('orders', { fkDistribution: { customer_id: 'zipf' } })
  .customize('line_items', { fkDistribution: { order_id: 'zipf', product_id: 'adversarial' } });

Multiple calls to customize() for the same table are merged — later calls add to earlier ones.