Binary search in Go

binarysearch.go

package binarysearch

import (
	"errors"
)

func BinarySearch(a []int, target int) (int, error) {
	startPos := 0
	endPos := len(a)

	for true {
		if startPos == endPos {
			return -1, errors.New("no target in the array")
		}

		mid := (endPos + startPos) / 2
		c := a[mid]

		if target == c {
			return mid, nil
		} else if target < c {
			endPos = mid
			continue
		} else {
			startPos = mid + 1
			continue
		}
	}

	return 0, nil
}

binearsearch_test.go

package binarysearch

import (
	"errors"
	"testing"
)

func TestBinarySearch1(t *testing.T) {
	a := []int{1, 2, 3, 4, 5}

	for i, v := range a {
		r, err := BinarySearch(a, v)
		if err != nil {
			t.Error(err)
		}
		if r != i {
			t.Error(errors.New("wrong"))
		}
	}
}

func TestBinarySearch2(t *testing.T) {
	a := []int{1, 2, 3, 4, 5}

	_, err := BinarySearch(a, 0)
	if err != nil {
		t.Log(err)
	} else {
		t.Error(errors.New("wrong"))
	}
}

func TestBinarySearch3(t *testing.T) {
	a := []int{1, 2, 3, 4, 5}

	_, err := BinarySearch(a, 6)
	if err != nil {
		t.Log(err)
	} else {
		t.Error(errors.New("wrong"))
	}
}

func TestBinarySearch4(t *testing.T) {
	a := []int{1, 2, 3, 4, 5, 6}

	for i, v := range a {
		r, err := BinarySearch(a, v)
		if err != nil {
			t.Error(err)
		}
		if r != i {
			t.Error(errors.New("wrong"))
		}
	}
}

func TestBinarySearch5(t *testing.T) {
	a := []int{1}

	for i, v := range a {
		r, err := BinarySearch(a, v)
		if err != nil {
			t.Error(err)
		}
		if r != i {
			t.Error(errors.New("wrong"))
		}
	}
}

func TestBinarySearch6(t *testing.T) {
	a := []int{}

	for i, v := range a {
		r, err := BinarySearch(a, v)
		if err != nil {
			t.Error(err)
		}
		if r != i {
			t.Error(errors.New("wrong"))
		}
	}
}