Class: Pbt::Arbitrary::ArrayArbitrary

Inherits:
Arbitrary
  • Object
show all
Defined in:
lib/pbt/arbitrary/array_arbitrary.rb

Overview

Generates arrays of values generated by ‘value_arb` with type `T`.

Instance Method Summary collapse

Methods inherited from Arbitrary

#filter, #map

Constructor Details

#initialize(value_arb, min_length = 0, max_length = DEFAULT_MAX_SIZE) ⇒ ArrayArbitrary

Returns a new instance of ArrayArbitrary.

Parameters:

  • value_arb (Arbitrary) —

    Arbitrary to generate values.

  • min_length (Integer) (defaults to: 0) —

    Minimum length of the generated array. Default is 0.

  • max_length (Integer) (defaults to: DEFAULT_MAX_SIZE) —

    Maximum length of the generated array. Default is 10.

Raises:

  • (ArgumentError) 


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# File 'lib/pbt/arbitrary/array_arbitrary.rb', line 13

def initialize(value_arb, min_length = 0, max_length = DEFAULT_MAX_SIZE)
  raise ArgumentError, "min_length must be zero or positive number" if min_length < 0

  @min_length = min_length
  @max_length = max_length
  @value_arb = value_arb
  @length_arb = IntegerArbitrary.new(min_length, max_length)
end

Instance Method Details

#generate(rng) ⇒ Object

See Also:



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# File 'lib/pbt/arbitrary/array_arbitrary.rb', line 23

def generate(rng)
  length = @length_arb.generate(rng)
  length.times.map { @value_arb.generate(rng) }
end

#shrink(current) ⇒ Object

See Also:



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# File 'lib/pbt/arbitrary/array_arbitrary.rb', line 29

def shrink(current)
  return Enumerator.new { |_| } if current.size == @min_length

  Enumerator.new do |y|
    # First, shrink the length of the array and try combinations of elements.
    # But this doesn't try all possible combinations since it'd be too huge and slow.
    @length_arb.shrink(current.size).each do |length|
      if length == 0
        y.yield []
        next
      end
      current.each_cons(length) do |con|
        y.yield con
      end
    end

    # Second, shrink each element of the array.
    current.each_with_index do |item, i|
      @value_arb.shrink(item).each do |val|
        y.yield [*current[...i], val, *current[i + 1..]]
      end
    end
  end
end