Default Values for Built-in Arbitraries

Every Arbitrary has a default value. When repeatTest runs, it tests the default value first as a smoke test before generating random values.

This table shows the default values for common Arbitraries:

Arbitrary	Code	Default Value
int (positive range)	`arb.int(1, 100)`	`1`
int (negative range)	`arb.int(-100, -1)`	`-1`
int (spans zero)	`arb.int(-100, 100)`	`0`
int32	`arb.int32()`	`0`
safeInt	`arb.safeInt()`	`0`
boolean	`arb.boolean()`	`false`
biased	`arb.biased(0.9)`	`false`
string	`arb.string()`	`""`
wellFormedString	`arb.wellFormedString()`	`""`
asciiLetter	`arb.asciiLetter()`	`"a"`
asciiDigit	`arb.asciiDigit()`	`"0"`
asciiWhitespace	`arb.asciiWhitespace()`	`" "`
char16	`arb.char16()`	`"a"`
unicodeChar	`arb.unicodeChar()`	`"a"`
array	`arb.array(arb.int(0, 10))`	`[]`
array (fixed length)	`arb.array(arb.int(0, 10), { length: 3 })`	`[0,0,0]`
object	`arb.object({ a: arb.int(1, 5), b: arb.boolean() })`	`{"a":1,"b":false}`
of	`arb.of("a", "b", "c")`	`"a"`
oneOf	`arb.oneOf(arb.of(1), arb.of(2), arb.of(3))`	`1`

Notes

arb.int(min, max): Default is min for positive ranges, -1 for negative ranges, or 0 if the range spans zero.
arb.boolean(): Default is false.
arb.string() and other string arbitraries: Default is the empty string "".
arb.array(...): Default is an empty array [], unless a fixed length is specified.
arb.of(...): Default is the first value.
arb.oneOf(...): Default comes from the first case.
arb.object(...): Default has each property set to its arbitrary's default.

When writing custom Arbitraries with arb.from(), the default is determined by each nested pick() call returning its own default value.