quick_check.js

The quick_check.js Developer Hub

Welcome to the quick_check.js developer hub. You'll find comprehensive guides and documentation to help you start working with quick_check.js as quickly as possible, as well as support if you get stuck. Let's jump right in!

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Number Generators

These generators create numbers

Most number generators have a large variant which will generate larger numbers.

qc.ureal and qc.ureal.large

Generates a random positive number.

qc.real and qc.real.large

Generates a random number.

qc.uint and qc.uint.large

Generates a random positive integer.

qc.int and qc.int.large

Generates a random integer.

qc.int.between(min, max)

Generates a random integer falling between min and max.

qc.natural and qc.natural.large

Generates a random natural number (i.e. postive integer greater than zero).

qc.random

Generates a random number between 0 and 1.

qc.range([gen])

Generates an array of two numbers where the second is guaranteed to be greater than the first. Be default the numbers are supplied by qc.real, but you can customize the generator.

So for example qc.range(qc.natural) will generate a range of natural numbers.

qc.range.inclusive([gen])

Generates an array of two numbers where the second is guaranteed to be greater or equal than the first. Be default the numbers are supplied by qc.real, but you can customize the generator.

So for example qc.range.inclusive(qc.natural) will generate a range of natural numbers.

expect(function(arg) {
  return arg[0] < arg[1];
}).forAll(qc.range());

expect(function(arg) {
  return arg[0] <= arg[1];
}).forAll(qc.range.inclusive(qc.real));

expect(function(arg) {
  return (0 <= arg[0] && arg[0] < arg[1]);
}).forAll(qc.range(qc.ureal));

expect(function(arg) {
  return (0 < arg[0] && arg[0] < arg[1]);
}).forAll(qc.range(qc.natural));
expect(([min, max]) -> min < max).forAll(qc.range())

expect(([min, max]) -> min <= max).forAll(qc.range.inclusive(qc.real))

expect(([min, max]) -> 0 <= min < max).forAll(qc.range(qc.ureal))

expect(([min, max]) -> 0 < min < max).forAll(qc.range(qc.natural))
expect(([min, max]) => min < max).forAll(qc.range());

expect(([min, max]) => min <= max).forAll(qc.range.inclusive(qc.real));

expect(([min, max]) => 0 <= min && min < max).forAll(qc.range(qc.ureal));

expect(([min, max]) => 0 < min && min < max).forAll(qc.range(qc.natural));

qc.dice(diceDSL)

This generator is meant for generating integers, but particularly if the tests should use integers from a particular distribution.

It uses a D&D inspired language for generating distributions, which is quite intuitive, as it models dice. So d6 means roll a six sided die, 2d4 means roll two four sided dies and add up their results.

Here is an overview of the language:

Token
Explanation
Example

xdy

Roll x y-sided dice and add up their results.

4d6 - roll 4 six-sided dice, will yield an int between 4 and 24.

Fx

Flip x coins. If they all turn heads, count 1, otherwise 0.

F2 will be 1 with probability of 1/4.

a ? b : c

If a is greater than zero, evaluate to b, otherwise to c.

Useful especially with coin flips: F5 ? 3d3 : 1

+, -, *

Standard arithmetical operators

3d3 + 4d2

(, )

Brackets can be used to group operators. Bracketing operands to d and F operators isn't supported yet.

F5 ? (3d3 + 2) : 1

qc.dice('d3') === function() {
  return Math.ceil(qc.random() * 3);
};

qc.dice('d2 + d4 + 3') === function() {
  return Math.ceil(qc.random() * 2) + Math.ceil(qc.random() * 4) + 3;
};

qc.dice('2d6') === function() {
  return Math.ceil(qc.random() * 6) + Math.ceil(qc.random() * 6);
};
qc.dice('d3') == -> Math.ceil(qc.random() * 3)
qc.dice('d2 + d4 + 3') == ->
  Math.ceil(qc.random() * 2) + Math.ceil(qc.random() * 4) + 3
qc.dice('2d6') == ->
  Math.ceil(qc.random() * 6) + Math.ceil(qc.random() * 6)
qc.dice('d3') === ((size) => Math.ceil(qc.random() * 3))
qc.dice('d2 + d4 + 3') === ((size) => Math.ceil(qc.random() * 2) + Math.ceil(qc.random() * 4) + 3)
qc.dice('2d6') === ((size) => Math.ceil(qc.random() * 6) + Math.ceil(qc.random() * 6))

Number Generators

These generators create numbers