module PropCheck::Generators
Contains common generators. Use this module by including it in the class (e.g. in your test suite) where you want to use them.
Public Instance Methods
Generates a single-character string containing one of a..z, A..Z, 0..9
Shrinks towards lowercase 'a'.
>> Generators.alphanumeric_char.sample(5, size: 10, rng: Random.new(42)) => ["M", "Z", "C", "o", "Q"]
# File lib/prop_check/generators.rb, line 361 def alphanumeric_char one_of(*@@alphanumeric_chars.map(&method(:constant))) end
Generates a string containing only the characters a..z, A..Z, 0..9
Shrinks towards fewer characters, and towards lowercase 'a'.
>> Generators.alphanumeric_string.sample(5, size: 10, rng: Random.new(42)) => ["ZCoQ", "8uM", "wkkx0JNx", "v0bxRDLb", "Gl5v8RyWA6"]
Accepts the same options as `array`
# File lib/prop_check/generators.rb, line 375 def alphanumeric_string(**kwargs) array(alphanumeric_char, **kwargs).map(&:join) end
Generates an array of elements, where each of the elements is generated by `element_generator`.
Shrinks to shorter arrays (with shrunken elements). Accepted keyword arguments:
`empty:` When false, behaves the same as `min: 1` `min:` Ensures at least this many elements are generated. (default: 0) `max:` Ensures at most this many elements are generated. When nil, an arbitrary count is used instead. (default: nil) `uniq:` When `true`, ensures that all elements in the array are unique.
When given a proc, uses the result of this proc to check for uniqueness. (matching the behaviour of `Array#uniq`) If it is not possible to generate another unique value after the configured `max_consecutive_attempts` an `PropCheck::Errors::GeneratorExhaustedError` will be raised. (default: `false`) >> Generators.array(Generators.positive_integer).sample(5, size: 1, rng: Random.new(42)) => [[2], [2], [2], [1], [2]] >> Generators.array(Generators.positive_integer).sample(5, size: 10, rng: Random.new(42)) => [[10, 5, 1, 4], [5, 9, 1, 1, 11, 8, 4, 9, 11, 10], [6], [11, 11, 2, 2, 7, 2, 6, 5, 5], [2, 10, 9, 7, 9, 5, 11, 3]] >> Generators.array(Generators.positive_integer, empty: true).sample(5, size: 1, rng: Random.new(1)) => [[], [2], [], [], [2]] >> Generators.array(Generators.positive_integer, empty: false).sample(5, size: 1, rng: Random.new(1)) => [[2], [1], [2], [1], [1]] >> Generators.array(Generators.boolean, uniq: true).sample(5, rng: Random.new(1)) => [[true, false], [false, true], [true, false], [false, true], [false, true]]
# File lib/prop_check/generators.rb, line 265 def array(element_generator, min: 0, max: nil, empty: true, uniq: false) min = 1 if min.zero? && !empty uniq = proc { |x| x } if uniq == true if max.nil? nonnegative_integer.bind { |count| make_array(element_generator, min, count, uniq) } else make_array(element_generator, min, max, uniq) end end
Generates a single-character string from the printable ASCII character set.
Shrinks towards 'n'.
>> Generators.ascii_char.sample(size: 10, rng: Random.new(42)) => ["d", "S", "|", ".", "g", "\\", "4", "d", "r", "v"]
# File lib/prop_check/generators.rb, line 430 def ascii_char one_of(*@@ascii_chars.map(&method(:constant))) end
Generates strings from the printable ASCII character set.
Shrinks towards fewer characters, and towards 'n'.
>> Generators.ascii_string.sample(5, size: 10, rng: Random.new(42)) => ["S|.g", "drvjjw\b\a7\"", "!w=E!_[4@k", "x", "zZI{[o"]
Accepts the same options as `array`
# File lib/prop_check/generators.rb, line 444 def ascii_string(**kwargs) array(ascii_char, **kwargs).map(&:join) end
Generates either `true` or `false`
Shrinks towards `false`
>> Generators.boolean.sample(5, size: 10, rng: Random.new(42)) => [false, true, false, false, false]
# File lib/prop_check/generators.rb, line 516 def boolean one_of(constant(false), constant(true)) end
Generates a single unicode character (both printable and non-printable).
Shrinks towards characters with lower codepoints, e.g. ASCII
>> Generators.printable_char.sample(size: 10, rng: Random.new(42)) => ["吏", "", "", "", "", "", "", "", "", "Ȍ"]
# File lib/prop_check/generators.rb, line 489 def char choose(0..0x10FFFF).map do |num| [num].pack('U') end end
Returns a random integer in the given range (if a range is given) or between 0..num (if a single integer is given).
Does not scale when `size` changes. This means `choose` is useful for e.g. picking an element out of multiple possibilities, but for other purposes you probably want to use `integer` et co.
Shrinks to integers closer to zero.
>> r = Random.new(42); Generators.choose(0..5).sample(size: 10, rng: r) => [3, 4, 2, 4, 4, 1, 2, 2, 2, 4] >> r = Random.new(42); Generators.choose(0..5).sample(size: 20000, rng: r) => [3, 4, 2, 4, 4, 1, 2, 2, 2, 4]
# File lib/prop_check/generators.rb, line 62 def choose(range) Generator.new do |rng:, **| val = rng.rand(range) LazyTree.new(val, integer_shrink(val)) end end
Always returns the same value, regardless of `size` or `rng` (random number generator state)
No shrinking (only considers the current single value `val`).
>> Generators.constant("pie").sample(5, size: 10, rng: Random.new(42)) => ["pie", "pie", "pie", "pie", "pie"]
# File lib/prop_check/generators.rb, line 21 def constant(val) Generator.wrap(val) end
Generates `nil` or `false`.
Shrinks towards `nil`.
>> Generators.falsey.sample(5, size: 10, rng: Random.new(42)) => [nil, false, nil, nil, nil]
# File lib/prop_check/generators.rb, line 538 def falsey one_of(constant(nil), constant(false)) end
Given a `hash` where the values are generators, creates a generator that returns hashes with the same keys, and their corresponding values from their corresponding generators.
Shrinks element generators.
>> Generators.fixed_hash(a: Generators.integer(), b: Generators.real_float(), c: Generators.integer()).call(size: 10, rng: Random.new(42)) => {:a=>-4, :b=>13.0, :c=>-3}
# File lib/prop_check/generators.rb, line 224 def fixed_hash(hash) keypair_generators = hash.map do |key, generator| generator.map { |val| [key, val] } end tuple(*keypair_generators) .map(&:to_h) end
Generates floating-point numbers Will generate NaN, Infinity, -Infinity, as well as Float::EPSILON, Float::MAX, Float::MIN, 0.0.next_float, 0.0.prev_float, to test the handling of floating-point edge cases. Approx. 1/100 generated numbers is a special one.
Shrinks to smaller, real floats.
>> Generators.float().sample(10, size: 10, rng: Random.new(42)) => [4.0, 9.555555555555555, 0.0, -Float::INFINITY, 5.5, -5.818181818181818, 1.1428571428571428, 0.0, 8.0, 7.857142857142858]
# File lib/prop_check/generators.rb, line 161 def float frequency(99 => real_float, 1 => one_of(*@@special_floats.map(&method(:constant)))) end
Picks one of the choices given in `frequencies` at random every time. `frequencies` expects keys to be numbers (representing the relative frequency of this generator) and values to be generators.
Side note: If you want to use the same frequency number for multiple generators, Ruby syntax requires you to send an array of two-element arrays instead of a hash.
Shrinks to arbitrary elements (since hashes are not ordered).
>> Generators.frequency(5 => Generators.integer, 1 => Generators.printable_ascii_char).sample(size: 10, rng: Random.new(42)) => [4, -3, 10, 8, 0, -7, 10, 1, "E", 10]
# File lib/prop_check/generators.rb, line 191 def frequency(frequencies) choices = frequencies.reduce([]) do |acc, elem| freq, val = elem acc + ([val] * freq) end one_of(*choices) end
Generates a hash of key->values, where each of the keys is made using the `key_generator` and each of the values using the `value_generator`.
Shrinks to hashes with less key/value pairs.
>> Generators.hash(Generators.printable_ascii_string, Generators.positive_integer).sample(5, size: 3, rng: Random.new(42)) => [{""=>2, "g\\4"=>4, "rv"=>2}, {"7"=>2}, {"!"=>1, "E!"=>1}, {"kY5"=>2}, {}]
# File lib/prop_check/generators.rb, line 335 def hash(*args, **kwargs) if args.length == 2 hash_of(*args, **kwargs) else super end end
Alias for `#hash` that does not conflict with a possibly overriden `Object#hash`.
# File lib/prop_check/generators.rb, line 347 def hash_of(key_generator, value_generator, **kwargs) array(tuple(key_generator, value_generator), **kwargs) .map(&:to_h) end
Generates an instance of `klass` using `args` and/or `kwargs` as generators for the arguments that are passed to `klass.new`
## Example:
Given a class like this:
class User attr_accessor :name, :age def initialize(name: , age: ) @name = name @age = age end def inspect "<User name: #{@name.inspect}, age: #{@age.inspect}>" end end >> user_gen = Generators.instance(User, name: Generators.printable_ascii_string, age: Generators.nonnegative_integer) >> user_gen.sample(3, rng: Random.new(42)).inspect => "[<User name: \"S|.g\", age: 10>, <User name: \"rvjj\", age: 10>, <User name: \"7\\\"5T!w=\", age: 5>]"
# File lib/prop_check/generators.rb, line 616 def instance(klass, *args, **kwargs) tuple(*args).bind do |vals| fixed_hash(**kwargs).map do |kwvals| if kwvals == {} klass.new(*vals) elsif vals == [] klass.new(**kwvals) else klass.new(*vals, **kwvals) end end end end
A random integer which scales with `size`. Integers start small (around 0) and become more extreme (both higher and lower, negative) when `size` increases.
Shrinks to integers closer to zero.
>> Generators.integer.call(size: 2, rng: Random.new(42)) => 1 >> Generators.integer.call(size: 10000, rng: Random.new(42)) => 5795 >> r = Random.new(42); Generators.integer.sample(size: 20000, rng: r) => [-4205, -19140, 18158, -8716, -13735, -3150, 17194, 1962, -3977, -18315]
# File lib/prop_check/generators.rb, line 83 def integer Generator.new do |size:, rng:, **| ensure_proper_size!(size) val = rng.rand(-size..size) LazyTree.new(val, integer_shrink(val)) end end
Only returns integers that are smaller than zero. See `integer` for more information.
# File lib/prop_check/generators.rb, line 122 def negative_integer positive_integer.map(&:-@) end
Generates always `nil`.
Does not shrink.
>> Generators.nil.sample(5, size: 10, rng: Random.new(42)) => [nil, nil, nil, nil, nil]
# File lib/prop_check/generators.rb, line 527 def nil constant(nil) end
Generates whatever `other_generator` generates but sometimes instead `nil`.`
>> Generators.nillable(Generators.integer).sample(20, size: 10, rng: Random.new(42)) => [9, 10, 8, 0, 10, -3, -8, 10, 1, -9, -10, nil, 1, 6, nil, 1, 9, -8, 8, 10]
# File lib/prop_check/generators.rb, line 587 def nillable(other_generator) frequency(9 => other_generator, 1 => constant(nil)) end
Only returns integers that are zero or larger. See `integer` for more information.
# File lib/prop_check/generators.rb, line 101 def nonnegative_integer integer.map(&:abs) end
Only returns integers that are zero or smaller. See `integer` for more information.
# File lib/prop_check/generators.rb, line 115 def nonpositive_integer nonnegative_integer.map(&:-@) end
Picks one of the given generators in `choices` at random uniformly every time.
Shrinks to values earlier in the list of `choices`.
>> Generators.one_of(Generators.constant(true), Generators.constant(false)).sample(5, size: 10, rng: Random.new(42)) => [true, false, true, true, true]
# File lib/prop_check/generators.rb, line 172 def one_of(*choices) choose(choices.length).bind do |index| choices[index] end end
Only returns integers that are larger than zero. See `integer` for more information.
# File lib/prop_check/generators.rb, line 108 def positive_integer nonnegative_integer.map { |x| x + 1 } end
Generates a single-character string from the printable ASCII character set.
Shrinks towards ' '.
>> Generators.printable_ascii_char.sample(size: 10, rng: Random.new(42)) => ["S", "|", ".", "g", "\\", "4", "r", "v", "j", "j"]
# File lib/prop_check/generators.rb, line 389 def printable_ascii_char one_of(*@@printable_ascii_chars.map(&method(:constant))) end
Generates strings from the printable ASCII character set.
Shrinks towards fewer characters, and towards ' '.
>> Generators.printable_ascii_string.sample(5, size: 10, rng: Random.new(42)) => ["S|.g", "rvjjw7\"5T!", "=", "!_[4@", "Y"]
Accepts the same options as `array`
# File lib/prop_check/generators.rb, line 403 def printable_ascii_string(**kwargs) array(printable_ascii_char, **kwargs).map(&:join) end
Generates a single-character printable string both ASCII characters and Unicode.
Shrinks towards characters with lower codepoints, e.g. ASCII
>> Generators.printable_char.sample(size: 10, rng: Random.new(42)) => ["吏", "", "", "", "", "", "", "", "", "Ȍ"]
# File lib/prop_check/generators.rb, line 463 def printable_char one_of(*@@printable_chars.map(&method(:constant))) end
Generates a printable string both ASCII characters and Unicode.
Shrinks towards shorter strings, and towards characters with lower codepoints, e.g. ASCII
>> Generators.printable_string.sample(5, size: 10, rng: Random.new(42)) => ["", "Ȍ", "𐁂", "Ȕ", ""]
Accepts the same options as `array`
# File lib/prop_check/generators.rb, line 477 def printable_string(**kwargs) array(printable_char, **kwargs).map(&:join) end
Generates floating-point numbers These start small (around 0) and become more extreme (large positive and large negative numbers)
Will only generate 'reals', that is: no infinity, no NaN, no numbers testing the limits of floating-point arithmetic.
Shrinks to numbers closer to zero.
>> Generators.real_float().sample(10, size: 10, rng: Random.new(42)) => [-2.2, -0.2727272727272727, 4.0, 1.25, -3.7272727272727275, -8.833333333333334, -8.090909090909092, 1.1428571428571428, 0.0, 8.0]
# File lib/prop_check/generators.rb, line 143 def real_float tuple(integer, integer, integer).map do |a, b, c| fraction(a, b, c) end end
Generates symbols consisting of lowercase letters and potentially underscores.
Shrinks towards shorter symbols and the letter 'a'.
>> Generators.simple_symbol.sample(5, size: 10, rng: Random.new(42)) => [:tokh, :gzswkkxudh, :vubxlfbu, :lzvlyq__jp, :oslw]
# File lib/prop_check/generators.rb, line 549 def simple_symbol alphabet = ('a'..'z').to_a alphabet << '_' array(one_of(*alphabet.map(&method(:constant)))) .map(&:join) .map(&:to_sym) end
Generates a string of unicode characters (which might contain both printable and non-printable characters).
Shrinks towards characters with lower codepoints, e.g. ASCII
>> Generators.string.sample(5, size: 10, rng: Random.new(42)) => ["\u{A3DB3}𠍜\u{3F46A}\u{1AEBC}", "𡡹\u{DED74}𪱣\u{43E97}ꂂ\u{50695}\u{C0301}", "\u{4FD9D}", "\u{C14BF}\u{193BB}𭇋\u{76B58}", "𦐺\u{9FDDB}\u{80ABB}\u{9E3CF}𐂽\u{14AAE}"]
Accepts the same options as `array`
# File lib/prop_check/generators.rb, line 505 def string(**kwargs) array(char, **kwargs).map(&:join) end
Generates common terms that are not `nil` or `false`.
Shrinks towards simpler terms, like `true`, an empty array, a single character or an integer.
>> Generators.truthy.sample(5, size: 10, rng: Random.new(42)) => [[4, 0, -3, 10, -4, 8, 0, 0, 10], -3, [5.5, -5.818181818181818, 1.1428571428571428, 0.0, 8.0, 7.857142857142858, -0.6666666666666665, 5.25], [], ["\u{9E553}\u{DD56E}\u{A5BBB}\u{8BDAB}\u{3E9FC}\u{C4307}\u{DAFAE}\u{1A022}\u{938CD}\u{70631}", "\u{C4C01}\u{32D85}\u{425DC}"]]
# File lib/prop_check/generators.rb, line 564 def truthy one_of(constant(true), constant([]), char, integer, float, string, array(integer), array(float), array(char), array(string), hash(simple_symbol, integer), hash(string, integer), hash(string, string) ) end
Generates an array containing always exactly one value from each of the passed generators, in the same order as specified:
Shrinks element generators, one at a time (trying last one first).
>> Generators.tuple(Generators.integer, Generators.real_float).call(size: 10, rng: Random.new(42)) => [-4, 13.0]
# File lib/prop_check/generators.rb, line 207 def tuple(*generators) Generator.new do |**kwargs| LazyTree.zip(generators.map do |generator| generator.generate(**kwargs) end) end end
Private Instance Methods
# File lib/prop_check/generators.rb, line 92 def ensure_proper_size!(size) return if size.is_a?(Integer) && size >= 0 raise ArgumentError, "`size:` should be a nonnegative integer but got `#{size.inspect}`" end
# File lib/prop_check/generators.rb, line 126 def fraction(num_a, num_b, num_c) num_a.to_f + num_b.to_f / (num_c.to_f.abs + 1.0) end
# File lib/prop_check/generators.rb, line 25 def integer_shrink(val) # 0 cannot shrink further; base case return [] if val.zero? # Numbers are shrunken by # subtracting themselves, their half, quarter, eight, ... (rounded towards zero!) # from themselves, until the number itself is reached. # So: for 20 we have [0, 10, 15, 18, 19, 20] halvings = Helper .scanl(val) { |x| (x / 2.0).truncate } .take_while { |x| !x.zero? } .map { |x| val - x } .map { |x| LazyTree.new(x, integer_shrink(x)) } # For negative numbers, we also attempt if the positive number has the same result. if val.abs > val [LazyTree.new(val.abs, halvings)].lazy else halvings end end
# File lib/prop_check/generators.rb, line 276 def make_array(element_generator, min, count, uniq) amount = min if count < min amount = min if count == min && min != 0 amount ||= (count - min) # Simple, optimized implementation: return make_array_simple(element_generator, amount) unless uniq # More complex implementation that filters duplicates make_array_uniq(element_generator, min, amount, uniq) end
# File lib/prop_check/generators.rb, line 288 def make_array_simple(element_generator, amount) generators = amount.times.map do element_generator.clone end tuple(*generators) end
# File lib/prop_check/generators.rb, line 296 def make_array_uniq(element_generator, min, amount, uniq_fun) Generator.new do |**kwargs| arr = [] uniques = Set.new count = 0 (0..).lazy.map do elem = element_generator.clone.generate(**kwargs) if uniques.add?(uniq_fun.call(elem.root)) arr.push(elem) count = 0 else count += 1 end if count > kwargs[:max_consecutive_attempts] if arr.size >= min # Give up and return shorter array in this case amount = min else raise Errors::GeneratorExhaustedError, "Too many consecutive elements filtered by 'uniq:'." end end end .take_while { arr.size < amount } .force LazyTree.zip(arr).map { |array| array.uniq(&uniq_fun) } end end