coverage_test.go

package coverage

import (
	"github.com/leanovate/gopter"
)

func CoverageGen(mod uint32, count uint32) gopter.Gen {
	return func(params *gopter.GenParameters) *gopter.GenResult {
		coverage := make([][]uint32, count)

		for i := range coverage {
			n := int(uint64(mod/3) + params.NextUint64()%uint64(mod/3))
			set := make(map[uint32]struct{}, n)
			coverage[i] = make([]uint32, 0, n)
			for len(set) < n {
				x := uint32(params.NextUint64() % uint64(mod))
				if _, ok := set[x]; !ok {
					coverage[i] = append(coverage[i], x)
					set[x] = struct{}{}
				}
			}
		}

		return gopter.NewGenResult(coverage, CoverageShrinker)
	}
}

type coverageShrink struct {
	coverage [][]uint32
}

func CoverageShrinker(coverage interface{}) gopter.Shrink {

	shrink := coverageShrink{coverage.([][]uint32)}

	return shrink.Next
}

func (cs *coverageShrink) Next() (interface{}, bool) {
	cs.coverage = cs.coverage[:len(cs.coverage)/2]
	if len(cs.coverage) == 0 {

		return nil, false
	}

	return cs.coverage, true
}