bitset_test.go

// Copyright 2014 Will Fitzgerald. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

// This file tests bit sets

package bitset

import (
	"bytes"
	"compress/gzip"
	"encoding"
	"encoding/base64"
	"encoding/binary"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"math"
	"math/rand"
	"strconv"
	"testing"
)

func TestStringer(t *testing.T) {
	v := New(0)
	for i := uint(0); i < 10; i++ {
		v.Set(i)
	}
	if v.String() != "{0,1,2,3,4,5,6,7,8,9}" {
		t.Error("bad string output")
	}
}

func TestStringLong(t *testing.T) {
	v := New(0)
	for i := uint(0); i < 262145; i++ {
		v.Set(i)
	}
	str := v.String()
	if len(str) != 1723903 {
		t.Error("Unexpected string length: ", len(str))
	}
}

func TestEmptyBitSet(t *testing.T) {
	defer func() {
		if r := recover(); r != nil {
			t.Error("A zero-length bitset should be fine")
		}
	}()
	b := New(0)
	if b.Len() != 0 {
		t.Errorf("Empty set should have capacity 0, not %d", b.Len())
	}
}

func TestZeroValueBitSet(t *testing.T) {
	defer func() {
		if r := recover(); r != nil {
			t.Error("A zero-length bitset should be fine")
		}
	}()
	var b BitSet
	if b.Len() != 0 {
		t.Errorf("Empty set should have capacity 0, not %d", b.Len())
	}
}

func TestBitSetNew(t *testing.T) {
	v := New(16)
	if v.Test(0) {
		t.Errorf("Unable to make a bit set and read its 0th value.")
	}
}

func TestBitSetHuge(t *testing.T) {
	v := New(uint(math.MaxUint32))
	if v.Test(0) {
		t.Errorf("Unable to make a huge bit set and read its 0th value.")
	}
}

func TestLen(t *testing.T) {
	v := New(1000)
	if v.Len() != 1000 {
		t.Errorf("Len should be 1000, but is %d.", v.Len())
	}
}

func TestLenIsNumberOfBitsNotBytes(t *testing.T) {
	var b BitSet
	if b.Len() != 0 {
		t.Errorf("empty bitset should have Len 0, got %v", b.Len())
	}

	b.Set(0)
	if b.Len() != 1 {
		t.Errorf("bitset with first bit set should have Len 1, got %v", b.Len())
	}

	b.Set(8)
	if b.Len() != 9 {
		t.Errorf("bitset with 0th and 8th bit set should have Len 9, got %v", b.Len())
	}

	b.Set(1)
	if b.Len() != 9 {
		t.Errorf("bitset with 0th, 1st and 8th bit set should have Len 9, got %v", b.Len())
	}
}

func ExampleBitSet_Len() {
	var b BitSet
	b.Set(8)
	fmt.Println("len", b.Len())
	fmt.Println("count", b.Count())
	// Output:
	// len 9
	// count 1
}

func TestBitSetIsClear(t *testing.T) {
	v := New(1000)
	for i := uint(0); i < 1000; i++ {
		if v.Test(i) {
			t.Errorf("Bit %d is set, and it shouldn't be.", i)
		}
	}
}

func TestExtendOnBoundary(t *testing.T) {
	v := New(32)
	defer func() {
		if r := recover(); r != nil {
			t.Error("Border out of index error should not have caused a panic")
		}
	}()
	v.Set(32)
}

func TestExceedCap(t *testing.T) {
	defer func() {
		if r := recover(); r == nil {
			t.Error("Set to capacity should have caused a panic")
		}
	}()
	NumHosts := uint(32768)
	bmp := New(NumHosts)
	bmp.ClearAll()
	d := Cap()
	bmp.Set(d)

}

func TestExpand(t *testing.T) {
	v := New(0)
	defer func() {
		if r := recover(); r != nil {
			t.Error("Expansion should not have caused a panic")
		}
	}()
	for i := uint(0); i < 1000; i++ {
		v.Set(i)
	}
}

func TestBitSetAndGet(t *testing.T) {
	v := New(1000)
	v.Set(100)
	if !v.Test(100) {
		t.Errorf("Bit %d is clear, and it shouldn't be.", 100)
	}
}

func TestNextClear(t *testing.T) {
	v := New(1000)
	v.Set(0).Set(1)
	next, found := v.NextClear(0)
	if !found || next != 2 {
		t.Errorf("Found next clear bit as %d, it should have been 2", next)
	}

	v = New(1000)
	for i := uint(0); i < 66; i++ {
		v.Set(i)
	}
	next, found = v.NextClear(0)
	if !found || next != 66 {
		t.Errorf("Found next clear bit as %d, it should have been 66", next)
	}

	v = New(1000)
	for i := uint(0); i < 64; i++ {
		v.Set(i)
	}
	v.Clear(45)
	v.Clear(52)
	next, found = v.NextClear(10)
	if !found || next != 45 {
		t.Errorf("Found next clear bit as %d, it should have been 45", next)
	}

	v = New(1000)
	for i := uint(0); i < 128; i++ {
		v.Set(i)
	}
	v.Clear(73)
	v.Clear(99)
	next, found = v.NextClear(10)
	if !found || next != 73 {
		t.Errorf("Found next clear bit as %d, it should have been 73", next)
	}

	next, found = v.NextClear(72)
	if !found || next != 73 {
		t.Errorf("Found next clear bit as %d, it should have been 73", next)
	}
	next, found = v.NextClear(73)
	if !found || next != 73 {
		t.Errorf("Found next clear bit as %d, it should have been 73", next)
	}
	next, found = v.NextClear(74)
	if !found || next != 99 {
		t.Errorf("Found next clear bit as %d, it should have been 73", next)
	}

	v = New(128)
	next, found = v.NextClear(0)
	if !found || next != 0 {
		t.Errorf("Found next clear bit as %d, it should have been 0", next)
	}

	for i := uint(0); i < 128; i++ {
		v.Set(i)
	}
	_, found = v.NextClear(0)
	if found {
		t.Errorf("There are not clear bits")
	}

	b := new(BitSet)
	c, d := b.NextClear(1)
	if c != 0 || d {
		t.Error("Unexpected values")
		return
	}

	v = New(100)
	for i := uint(0); i != 100; i++ {
		v.Set(i)
	}
	next, found = v.NextClear(0)
	if found || next != 0 {
		t.Errorf("Found next clear bit as %d, it should have return (0, false)", next)

	}
}

func TestIterate(t *testing.T) {
	v := New(10000)
	v.Set(0)
	v.Set(1)
	v.Set(2)
	data := make([]uint, 3)
	c := 0
	for i, e := v.NextSet(0); e; i, e = v.NextSet(i + 1) {
		data[c] = i
		c++
	}
	if data[0] != 0 {
		t.Errorf("bug 0")
	}
	if data[1] != 1 {
		t.Errorf("bug 1")
	}
	if data[2] != 2 {
		t.Errorf("bug 2")
	}
	v.Set(10)
	v.Set(2000)
	data = make([]uint, 5)
	c = 0
	for i, e := v.NextSet(0); e; i, e = v.NextSet(i + 1) {
		data[c] = i
		c++
	}
	if data[0] != 0 {
		t.Errorf("bug 0")
	}
	if data[1] != 1 {
		t.Errorf("bug 1")
	}
	if data[2] != 2 {
		t.Errorf("bug 2")
	}
	if data[3] != 10 {
		t.Errorf("bug 3")
	}
	if data[4] != 2000 {
		t.Errorf("bug 4")
	}

}

func TestSetTo(t *testing.T) {
	v := New(1000)
	v.SetTo(100, true)
	if !v.Test(100) {
		t.Errorf("Bit %d is clear, and it shouldn't be.", 100)
	}
	v.SetTo(100, false)
	if v.Test(100) {
		t.Errorf("Bit %d is set, and it shouldn't be.", 100)
	}
}

func TestChain(t *testing.T) {
	if !New(1000).Set(100).Set(99).Clear(99).Test(100) {
		t.Errorf("Bit %d is clear, and it shouldn't be.", 100)
	}
}

func TestOutOfBoundsLong(t *testing.T) {
	v := New(64)
	defer func() {
		if r := recover(); r != nil {
			t.Error("Long distance out of index error should not have caused a panic")
		}
	}()
	v.Set(1000)
}

func TestOutOfBoundsClose(t *testing.T) {
	v := New(65)
	defer func() {
		if r := recover(); r != nil {
			t.Error("Local out of index error should not have caused a panic")
		}
	}()
	v.Set(66)
}

func TestCount(t *testing.T) {
	tot := uint(64*4 + 11) // just some multi unit64 number
	v := New(tot)
	checkLast := true
	for i := uint(0); i < tot; i++ {
		sz := uint(v.Count())
		if sz != i {
			t.Errorf("Count reported as %d, but it should be %d", sz, i)
			checkLast = false
			break
		}
		v.Set(i)
	}
	if checkLast {
		sz := uint(v.Count())
		if sz != tot {
			t.Errorf("After all bits set, size reported as %d, but it should be %d", sz, tot)
		}
	}
}

// test setting every 3rd bit, just in case something odd is happening
func TestCount2(t *testing.T) {
	tot := uint(64*4 + 11) // just some multi unit64 number
	v := New(tot)
	for i := uint(0); i < tot; i += 3 {
		sz := uint(v.Count())
		if sz != i/3 {
			t.Errorf("Count reported as %d, but it should be %d", sz, i)
			break
		}
		v.Set(i)
	}
}

// nil tests
func TestNullTest(t *testing.T) {
	var v *BitSet
	defer func() {
		if r := recover(); r == nil {
			t.Error("Checking bit of null reference should have caused a panic")
		}
	}()
	v.Test(66)
}

func TestNullSet(t *testing.T) {
	var v *BitSet
	defer func() {
		if r := recover(); r == nil {
			t.Error("Setting bit of null reference should have caused a panic")
		}
	}()
	v.Set(66)
}

func TestNullClear(t *testing.T) {
	var v *BitSet
	defer func() {
		if r := recover(); r == nil {
			t.Error("Clearning bit of null reference should have caused a panic")
		}
	}()
	v.Clear(66)
}

func TestNullCount(t *testing.T) {
	var v *BitSet
	defer func() {
		if r := recover(); r != nil {
			t.Error("Counting null reference should not have caused a panic")
		}
	}()
	cnt := v.Count()
	if cnt != 0 {
		t.Errorf("Count reported as %d, but it should be 0", cnt)
	}
}

func TestPanicDifferenceBNil(t *testing.T) {
	var b *BitSet
	var compare = New(10)
	defer func() {
		if r := recover(); r == nil {
			t.Error("Nil First should should have caused a panic")
		}
	}()
	b.Difference(compare)
}

func TestPanicDifferenceCompareNil(t *testing.T) {
	var compare *BitSet
	var b = New(10)
	defer func() {
		if r := recover(); r == nil {
			t.Error("Nil Second should should have caused a panic")
		}
	}()
	b.Difference(compare)
}

func TestPanicUnionBNil(t *testing.T) {
	var b *BitSet
	var compare = New(10)
	defer func() {
		if r := recover(); r == nil {
			t.Error("Nil First should should have caused a panic")
		}
	}()
	b.Union(compare)
}

func TestPanicUnionCompareNil(t *testing.T) {
	var compare *BitSet
	var b = New(10)
	defer func() {
		if r := recover(); r == nil {
			t.Error("Nil Second should should have caused a panic")
		}
	}()
	b.Union(compare)
}

func TestPanicIntersectionBNil(t *testing.T) {
	var b *BitSet
	var compare = New(10)
	defer func() {
		if r := recover(); r == nil {
			t.Error("Nil First should should have caused a panic")
		}
	}()
	b.Intersection(compare)
}

func TestPanicIntersectionCompareNil(t *testing.T) {
	var compare *BitSet
	var b = New(10)
	defer func() {
		if r := recover(); r == nil {
			t.Error("Nil Second should should have caused a panic")
		}
	}()
	b.Intersection(compare)
}

func TestPanicSymmetricDifferenceBNil(t *testing.T) {
	var b *BitSet
	var compare = New(10)
	defer func() {
		if r := recover(); r == nil {
			t.Error("Nil First should should have caused a panic")
		}
	}()
	b.SymmetricDifference(compare)
}

func TestPanicSymmetricDifferenceCompareNil(t *testing.T) {
	var compare *BitSet
	var b = New(10)
	defer func() {
		if r := recover(); r == nil {
			t.Error("Nil Second should should have caused a panic")
		}
	}()
	b.SymmetricDifference(compare)
}

func TestPanicComplementBNil(t *testing.T) {
	var b *BitSet
	defer func() {
		if r := recover(); r == nil {
			t.Error("Nil should should have caused a panic")
		}
	}()
	b.Complement()
}

func TestPanicAnytBNil(t *testing.T) {
	var b *BitSet
	defer func() {
		if r := recover(); r == nil {
			t.Error("Nil should should have caused a panic")
		}
	}()
	b.Any()
}

func TestPanicNonetBNil(t *testing.T) {
	var b *BitSet
	defer func() {
		if r := recover(); r == nil {
			t.Error("Nil should should have caused a panic")
		}
	}()
	b.None()
}

func TestPanicAlltBNil(t *testing.T) {
	var b *BitSet
	defer func() {
		if r := recover(); r == nil {
			t.Error("Nil should should have caused a panic")
		}
	}()
	b.All()
}

func TestAll(t *testing.T) {
	v := New(0)
	if !v.All() {
		t.Error("Empty sets should return true on All()")
	}
	v = New(2)
	v.SetTo(0, true)
	v.SetTo(1, true)
	if !v.All() {
		t.Error("Non-empty sets with all bits set should return true on All()")
	}
	v = New(2)
	if v.All() {
		t.Error("Non-empty sets with no bits set should return false on All()")
	}
	v = New(2)
	v.SetTo(0, true)
	if v.All() {
		t.Error("Non-empty sets with some bits set should return false on All()")
	}
}

func TestShrink(t *testing.T) {
	bs := New(10)
	bs.Set(0)
	bs.Shrink(63)
	if !bs.Test(0) {
		t.Error("0 should be set")
		return
	}
	b := New(0)

	b.Set(0)
	b.Set(1)
	b.Set(2)
	b.Set(3)
	b.Set(64)
	b.Compact()
	if !b.Test(0) {
		t.Error("0 should be set")
		return
	}
	if !b.Test(1) {
		t.Error("1 should be set")
		return
	}
	if !b.Test(2) {
		t.Error("2 should be set")
		return
	}
	if !b.Test(3) {
		t.Error("3 should be set")
		return
	}
	if !b.Test(64) {
		t.Error("64 should be set")
		return
	}

	b.Shrink(2)
	if !b.Test(0) {
		t.Error("0 should be set")
		return
	}
	if !b.Test(1) {
		t.Error("1 should be set")
		return
	}
	if !b.Test(2) {
		t.Error("2 should be set")
		return
	}
	if b.Test(3) {
		t.Error("3 should not be set")
		return
	}
	if b.Test(64) {
		t.Error("64 should not be set")
		return
	}

	b.Set(24)
	b.Shrink(100)
	if !b.Test(24) {
		t.Error("24 should be set")
		return
	}

	b.Set(127)
	b.Set(128)
	b.Set(129)
	b.Compact()
	if !b.Test(127) {
		t.Error("127 should be set")
		return
	}
	if !b.Test(128) {
		t.Error("128 should be set")
		return
	}
	if !b.Test(129) {
		t.Error("129 be set")
		return
	}

	b.Shrink(128)
	if !b.Test(127) {
		t.Error("127 should be set")
		return
	}
	if !b.Test(128) {
		t.Error("128 should be set")
		return
	}
	if b.Test(129) {
		t.Error("129 should not be set")
		return
	}

	b.Set(129)
	b.Shrink(129)
	if !b.Test(129) {
		t.Error("129 should be set")
		return
	}

	b.Set(1000)
	b.Set(2000)
	b.Set(3000)
	b.Shrink(3000)
	if len(b.set) != 3000/64+1 {
		t.Error("Wrong length of BitSet.set")
		return
	}
	if !b.Test(3000) {
		t.Error("3000 should be set")
		return
	}

	b.Shrink(2000)
	if len(b.set) != 2000/64+1 {
		t.Error("Wrong length of BitSet.set")
		return
	}
	if b.Test(3000) {
		t.Error("3000 should not be set")
		return
	}
	if !b.Test(2000) {
		t.Error("2000 should be set")
		return
	}
	if !b.Test(1000) {
		t.Error("1000 should be set")
		return
	}
	if !b.Test(24) {
		t.Error("24 should be set")
		return
	}

	b = New(110)
	b.Set(80)
	b.Shrink(70)
	for _, word := range b.set {
		if word != 0 {
			t.Error("word should be 0", word)
		}
	}
}

func TestInsertAtWithSet(t *testing.T) {
	b := New(0)
	b.Set(0)
	b.Set(1)
	b.Set(63)
	b.Set(64)
	b.Set(65)

	b.InsertAt(3)
	if !b.Test(0) {
		t.Error("0 should be set")
		return
	}
	if !b.Test(1) {
		t.Error("1 should be set")
		return
	}
	if b.Test(3) {
		t.Error("3 should not be set")
		return
	}
	if !b.Test(64) {
		t.Error("64 should be set")
		return
	}
	if !b.Test(65) {
		t.Error("65 should be set")
		return
	}
	if !b.Test(66) {
		t.Error("66 should be set")
		return
	}

}

func TestInsertAt(t *testing.T) {
	type testCase struct {
		input     []string
		insertIdx uint
		expected  []string
	}

	testCases := []testCase{
		{
			input: []string{
				"1111111111111111111111111111111111111111111111111111111111111111",
			},
			insertIdx: uint(62),
			expected: []string{
				"1011111111111111111111111111111111111111111111111111111111111111",
				"0000000000000000000000000000000000000000000000000000000000000001",
			},
		},
		{
			input: []string{
				"1111111111111111111111111111111111111111111111111111111111111111",
			},
			insertIdx: uint(63),
			expected: []string{
				"0111111111111111111111111111111111111111111111111111111111111111",
				"0000000000000000000000000000000000000000000000000000000000000001",
			},
		},
		{
			input: []string{
				"1111111111111111111111111111111111111111111111111111111111111111",
			},
			insertIdx: uint(0),
			expected: []string{
				"1111111111111111111111111111111111111111111111111111111111111110",
				"0000000000000000000000000000000000000000000000000000000000000001",
			},
		},
		{
			input: []string{
				"1111111111111111111111111111111111111111111111111111111111111111",
				"1111111111111111111111111111111111111111111111111111111111111111",
				"1111111111111111111111111111111111111111111111111111111111111111",
			},
			insertIdx: uint(70),
			expected: []string{
				"1111111111111111111111111111111111111111111111111111111111111111",
				"1111111111111111111111111111111111111111111111111111111110111111",
				"1111111111111111111111111111111111111111111111111111111111111111",
				"0000000000000000000000000000000000000000000000000000000000000001",
			},
		},
		{
			input: []string{
				"1111111111111111111111111111111111111111111111111111111111111111",
				"1111111111111111111111111111111111111111111111111111111111111111",
				"1111111111111111111111111111111111111111111111111111111111110000",
			},
			insertIdx: uint(70),
			expected: []string{
				"1111111111111111111111111111111111111111111111111111111111111111",
				"1111111111111111111111111111111111111111111111111111111110111111",
				"1111111111111111111111111111111111111111111111111111111111100001",
				"0000000000000000000000000000000000000000000000000000000000000001",
			},
		},
		{
			input: []string{
				"1111111111111111111111111111111111111111111111111111111111110000",
			},
			insertIdx: uint(10),
			expected: []string{
				"1111111111111111111111111111111111111111111111111111101111110000",
				"0000000000000000000000000000000000000000000000000000000000000001",
			},
		},
	}

	for _, tc := range testCases {
		var input []uint64
		for _, inputElement := range tc.input {
			parsed, _ := strconv.ParseUint(inputElement, 2, 64)
			input = append(input, parsed)
		}

		var expected []uint64
		for _, expectedElement := range tc.expected {
			parsed, _ := strconv.ParseUint(expectedElement, 2, 64)
			expected = append(expected, parsed)
		}

		b := From(input)
		b.InsertAt(tc.insertIdx)
		if len(b.set) != len(expected) {
			t.Error("Length of sets should be equal")
			return
		}
		for i := range b.set {
			if b.set[i] != expected[i] {
				t.Error("Unexpected results found in set")
				return
			}
		}
	}
}

func TestNone(t *testing.T) {
	v := New(0)
	if !v.None() {
		t.Error("Empty sets should return true on None()")
	}
	v = New(2)
	v.SetTo(0, true)
	v.SetTo(1, true)
	if v.None() {
		t.Error("Non-empty sets with all bits set should return false on None()")
	}
	v = New(2)
	if !v.None() {
		t.Error("Non-empty sets with no bits set should return true on None()")
	}
	v = New(2)
	v.SetTo(0, true)
	if v.None() {
		t.Error("Non-empty sets with some bits set should return false on None()")
	}
	v = new(BitSet)
	if !v.None() {
		t.Error("Empty sets should return true on None()")
	}
}

func TestEqual(t *testing.T) {
	a := New(100)
	b := New(99)
	c := New(100)
	if a.Equal(b) {
		t.Error("Sets of different sizes should be not be equal")
	}
	if !a.Equal(c) {
		t.Error("Two empty sets of the same size should be equal")
	}
	a.Set(99)
	c.Set(0)
	if a.Equal(c) {
		t.Error("Two sets with differences should not be equal")
	}
	c.Set(99)
	a.Set(0)
	if !a.Equal(c) {
		t.Error("Two sets with the same bits set should be equal")
	}
	if a.Equal(nil) {
		t.Error("The sets should be different")
	}
	a = New(0)
	b = New(0)
	if !a.Equal(b) {
		t.Error("Two empty set should be equal")
	}
	var x *BitSet
	var y *BitSet
	z := New(0)
	if !x.Equal(y) {
		t.Error("Two nil bitsets should be equal")
	}
	if x.Equal(z) {
		t.Error("Nil receiver bitset should not be equal to non-nil bitset")
	}
}

func TestUnion(t *testing.T) {
	a := New(100)
	b := New(200)
	for i := uint(1); i < 100; i += 2 {
		a.Set(i)
		b.Set(i - 1)
	}
	for i := uint(100); i < 200; i++ {
		b.Set(i)
	}
	if a.UnionCardinality(b) != 200 {
		t.Errorf("Union should have 200 bits set, but had %d", a.UnionCardinality(b))
	}
	if a.UnionCardinality(b) != b.UnionCardinality(a) {
		t.Errorf("Union should be symmetric")
	}

	c := a.Union(b)
	d := b.Union(a)
	if c.Count() != 200 {
		t.Errorf("Union should have 200 bits set, but had %d", c.Count())
	}
	if !c.Equal(d) {
		t.Errorf("Union should be symmetric")
	}
}

func TestInPlaceUnion(t *testing.T) {
	a := New(100)
	b := New(200)
	for i := uint(1); i < 100; i += 2 {
		a.Set(i)
		b.Set(i - 1)
	}
	for i := uint(100); i < 200; i++ {
		b.Set(i)
	}
	c := a.Clone()
	c.InPlaceUnion(b)
	d := b.Clone()
	d.InPlaceUnion(a)
	if c.Count() != 200 {
		t.Errorf("Union should have 200 bits set, but had %d", c.Count())
	}
	if d.Count() != 200 {
		t.Errorf("Union should have 200 bits set, but had %d", d.Count())
	}
	if !c.Equal(d) {
		t.Errorf("Union should be symmetric")
	}
}

func TestIntersection(t *testing.T) {
	a := New(100)
	b := New(200)
	for i := uint(1); i < 100; i += 2 {
		a.Set(i)
		b.Set(i - 1).Set(i)
	}
	for i := uint(100); i < 200; i++ {
		b.Set(i)
	}
	if a.IntersectionCardinality(b) != 50 {
		t.Errorf("Intersection should have 50 bits set, but had %d", a.IntersectionCardinality(b))
	}
	if a.IntersectionCardinality(b) != b.IntersectionCardinality(a) {
		t.Errorf("Intersection should be symmetric")
	}
	c := a.Intersection(b)
	d := b.Intersection(a)
	if c.Count() != 50 {
		t.Errorf("Intersection should have 50 bits set, but had %d", c.Count())
	}
	if !c.Equal(d) {
		t.Errorf("Intersection should be symmetric")
	}
}

func TestInplaceIntersection(t *testing.T) {
	a := New(100)
	b := New(200)
	for i := uint(1); i < 100; i += 2 {
		a.Set(i)
		b.Set(i - 1).Set(i)
	}
	for i := uint(100); i < 200; i++ {
		b.Set(i)
	}
	c := a.Clone()
	c.InPlaceIntersection(b)
	d := b.Clone()
	d.InPlaceIntersection(a)
	if c.Count() != 50 {
		t.Errorf("Intersection should have 50 bits set, but had %d", c.Count())
	}
	if d.Count() != 50 {
		t.Errorf("Intersection should have 50 bits set, but had %d", d.Count())
	}
	if !c.Equal(d) {
		t.Errorf("Intersection should be symmetric")
	}
}

func TestDifference(t *testing.T) {
	a := New(100)
	b := New(200)
	for i := uint(1); i < 100; i += 2 {
		a.Set(i)
		b.Set(i - 1)
	}
	for i := uint(100); i < 200; i++ {
		b.Set(i)
	}
	if a.DifferenceCardinality(b) != 50 {
		t.Errorf("a-b Difference should have 50 bits set, but had %d", a.DifferenceCardinality(b))
	}
	if b.DifferenceCardinality(a) != 150 {
		t.Errorf("b-a Difference should have 150 bits set, but had %d", b.DifferenceCardinality(a))
	}

	c := a.Difference(b)
	d := b.Difference(a)
	if c.Count() != 50 {
		t.Errorf("a-b Difference should have 50 bits set, but had %d", c.Count())
	}
	if d.Count() != 150 {
		t.Errorf("b-a Difference should have 150 bits set, but had %d", d.Count())
	}
	if c.Equal(d) {
		t.Errorf("Difference, here, should not be symmetric")
	}
}

func TestInPlaceDifference(t *testing.T) {
	a := New(100)
	b := New(200)
	for i := uint(1); i < 100; i += 2 {
		a.Set(i)
		b.Set(i - 1)
	}
	for i := uint(100); i < 200; i++ {
		b.Set(i)
	}
	c := a.Clone()
	c.InPlaceDifference(b)
	d := b.Clone()
	d.InPlaceDifference(a)
	if c.Count() != 50 {
		t.Errorf("a-b Difference should have 50 bits set, but had %d", c.Count())
	}
	if d.Count() != 150 {
		t.Errorf("b-a Difference should have 150 bits set, but had %d", d.Count())
	}
	if c.Equal(d) {
		t.Errorf("Difference, here, should not be symmetric")
	}
}

func TestSymmetricDifference(t *testing.T) {
	a := New(100)
	b := New(200)
	for i := uint(1); i < 100; i += 2 {
		a.Set(i)            // 01010101010 ... 0000000
		b.Set(i - 1).Set(i) // 11111111111111111000000
	}
	for i := uint(100); i < 200; i++ {
		b.Set(i)
	}
	if a.SymmetricDifferenceCardinality(b) != 150 {
		t.Errorf("a^b Difference should have 150 bits set, but had %d", a.SymmetricDifferenceCardinality(b))
	}
	if b.SymmetricDifferenceCardinality(a) != 150 {
		t.Errorf("b^a Difference should have 150 bits set, but had %d", b.SymmetricDifferenceCardinality(a))
	}

	c := a.SymmetricDifference(b)
	d := b.SymmetricDifference(a)
	if c.Count() != 150 {
		t.Errorf("a^b Difference should have 150 bits set, but had %d", c.Count())
	}
	if d.Count() != 150 {
		t.Errorf("b^a Difference should have 150 bits set, but had %d", d.Count())
	}
	if !c.Equal(d) {
		t.Errorf("SymmetricDifference should be symmetric")
	}
}

func TestInPlaceSymmetricDifference(t *testing.T) {
	a := New(100)
	b := New(200)
	for i := uint(1); i < 100; i += 2 {
		a.Set(i)            // 01010101010 ... 0000000
		b.Set(i - 1).Set(i) // 11111111111111111000000
	}
	for i := uint(100); i < 200; i++ {
		b.Set(i)
	}
	c := a.Clone()
	c.InPlaceSymmetricDifference(b)
	d := b.Clone()
	d.InPlaceSymmetricDifference(a)
	if c.Count() != 150 {
		t.Errorf("a^b Difference should have 150 bits set, but had %d", c.Count())
	}
	if d.Count() != 150 {
		t.Errorf("b^a Difference should have 150 bits set, but had %d", d.Count())
	}
	if !c.Equal(d) {
		t.Errorf("SymmetricDifference should be symmetric")
	}
}

func TestComplement(t *testing.T) {
	a := New(50)
	b := a.Complement()
	if b.Count() != 50 {
		t.Errorf("Complement failed, size should be 50, but was %d", b.Count())
	}
	a = New(50)
	a.Set(10).Set(20).Set(42)
	b = a.Complement()
	if b.Count() != 47 {
		t.Errorf("Complement failed, size should be 47, but was %d", b.Count())
	}
}

func TestIsSuperSet(t *testing.T) {
	test := func(name string, lenS, lenSS int, overrideS, overrideSS map[int]bool, want, wantStrict bool) {
		t.Run(name, func(t *testing.T) {
			s := New(uint(lenS))
			ss := New(uint(lenSS))

			l := lenS
			if lenSS < lenS {
				l = lenSS
			}

			r := rand.New(rand.NewSource(42))
			for i := 0; i < l; i++ {
				bit := r.Intn(2) == 1
				s.SetTo(uint(i), bit)
				ss.SetTo(uint(i), bit)
			}

			for i, v := range overrideS {
				s.SetTo(uint(i), v)
			}
			for i, v := range overrideSS {
				ss.SetTo(uint(i), v)
			}

			if got := ss.IsSuperSet(s); got != want {
				t.Errorf("IsSuperSet() = %v, want %v", got, want)
			}
			if got := ss.IsStrictSuperSet(s); got != wantStrict {
				t.Errorf("IsStrictSuperSet() = %v, want %v", got, wantStrict)
			}
		})
	}

	test("empty", 0, 0, nil, nil, true, false)
	test("empty vs non-empty", 0, 100, nil, nil, true, false)
	test("non-empty vs empty", 100, 0, nil, nil, true, false)
	test("equal", 100, 100, nil, nil, true, false)

	test("set is shorter, subset", 100, 200, map[int]bool{50: true}, map[int]bool{50: false}, false, false)
	test("set is shorter, equal", 100, 200, nil, nil, true, false)
	test("set is shorter, superset", 100, 200, map[int]bool{50: false}, map[int]bool{50: true}, true, true)
	test("set is shorter, neither", 100, 200, map[int]bool{50: true}, map[int]bool{50: false, 150: true}, false, false)

	test("set is longer, subset", 200, 100, map[int]bool{50: true}, map[int]bool{50: false}, false, false)
	test("set is longer, equal", 200, 100, nil, nil, true, false)
	test("set is longer, superset", 200, 100, nil, map[int]bool{150: true}, true, true)
	test("set is longer, neither", 200, 100, map[int]bool{50: false, 150: true}, map[int]bool{50: true}, false, false)
}

func TestDumpAsBits(t *testing.T) {
	a := New(10).Set(10)
	astr := "0000000000000000000000000000000000000000000000000000010000000000."
	if a.DumpAsBits() != astr {
		t.Errorf("DumpAsBits failed, output should be \"%s\" but was \"%s\"", astr, a.DumpAsBits())
	}
	var b BitSet // zero value (b.set == nil)
	bstr := "."
	if b.DumpAsBits() != bstr {
		t.Errorf("DumpAsBits failed, output should be \"%s\" but was \"%s\"", bstr, b.DumpAsBits())
	}
}

func TestMarshalUnmarshalBinary(t *testing.T) {
	a := New(1010).Set(10).Set(1001)
	b := new(BitSet)

	copyBinary(t, a, b)

	// BitSets must be equal after marshalling and unmarshalling
	if !a.Equal(b) {
		t.Error("Bitsets are not equal:\n\t", a.DumpAsBits(), "\n\t", b.DumpAsBits())
		return
	}

	aSetBit := uint(128)
	a = New(256).Set(aSetBit)
	aExpectedMarshaledSize := 8 /* length: uint64 */ + 4*8 /* set : [4]uint64 */
	aMarshaled, err := a.MarshalBinary()

	if err != nil || aExpectedMarshaledSize != len(aMarshaled) || aExpectedMarshaledSize != a.BinaryStorageSize() {
		t.Error("MarshalBinary failed to produce expected (", aExpectedMarshaledSize, ") number of bytes")
		return
	}

	shiftAmount := uint(72)
	// https://github.com/bits-and-blooms/bitset/issues/114
	for i := uint(0); i < shiftAmount; i++ {
		a.DeleteAt(0)
	}

	aExpectedMarshaledSize = 8 /* length: uint64 */ + 3*8 /* set : [3]uint64 */
	aMarshaled, err = a.MarshalBinary()
	if err != nil || aExpectedMarshaledSize != len(aMarshaled) || aExpectedMarshaledSize != a.BinaryStorageSize() {
		t.Error("MarshalBinary failed to produce expected (", aExpectedMarshaledSize, ") number of bytes")
		return
	}

	copyBinary(t, a, b)

	if b.Len() != 256-shiftAmount || !b.Test(aSetBit-shiftAmount) {
		t.Error("Shifted bitset is not copied correctly")
	}
}

func TestMarshalUnmarshalBinaryByLittleEndian(t *testing.T) {
	LittleEndian()
	defer func() {
		// Revert when done.
		binaryOrder = binary.BigEndian
	}()
	a := New(1010).Set(10).Set(1001)
	b := new(BitSet)

	copyBinary(t, a, b)

	// BitSets must be equal after marshalling and unmarshalling
	if !a.Equal(b) {
		t.Error("Bitsets are not equal:\n\t", a.DumpAsBits(), "\n\t", b.DumpAsBits())
		return
	}
}

func copyBinary(t *testing.T, from encoding.BinaryMarshaler, to encoding.BinaryUnmarshaler) {
	data, err := from.MarshalBinary()
	if err != nil {
		t.Errorf(err.Error())
		return
	}

	err = to.UnmarshalBinary(data)
	if err != nil {
		t.Errorf(err.Error())
		return
	}
}

func TestMarshalUnmarshalJSON(t *testing.T) {
	t.Run("value", func(t *testing.T) {
		a := BitSet{}
		a.Set(10).Set(1001)
		data, err := json.Marshal(a)
		if err != nil {
			t.Errorf(err.Error())
			return
		}

		b := new(BitSet)
		err = json.Unmarshal(data, b)
		if err != nil {
			t.Errorf(err.Error())
			return
		}

		// Bitsets must be equal after marshalling and unmarshalling
		if !a.Equal(b) {
			t.Error("Bitsets are not equal:\n\t", a.DumpAsBits(), "\n\t", b.DumpAsBits())
			return
		}
	})
	t.Run("pointer", func(t *testing.T) {
		a := New(1010).Set(10).Set(1001)
		data, err := json.Marshal(a)
		if err != nil {
			t.Errorf(err.Error())
			return
		}

		b := new(BitSet)
		err = json.Unmarshal(data, b)
		if err != nil {
			t.Errorf(err.Error())
			return
		}

		// Bitsets must be equal after marshalling and unmarshalling
		if !a.Equal(b) {
			t.Error("Bitsets are not equal:\n\t", a.DumpAsBits(), "\n\t", b.DumpAsBits())
			return
		}
	})
}

func TestMarshalUnmarshalJSONWithTrailingData(t *testing.T) {
	a := New(1010).Set(10).Set(1001)
	data, err := json.Marshal(a)
	if err != nil {
		t.Errorf(err.Error())
		return
	}

	// appending some noise
	data = data[:len(data)-3] // remove "
	data = append(data, []byte(`AAAAAAAAAA"`)...)

	b := new(BitSet)
	err = json.Unmarshal(data, b)
	if err != nil {
		t.Errorf(err.Error())
		return
	}

	// Bitsets must be equal after marshalling and unmarshalling
	// Do not over-reading when unmarshalling
	if !a.Equal(b) {
		t.Error("Bitsets are not equal:\n\t", a.DumpAsBits(), "\n\t", b.DumpAsBits())
		return
	}
}

func TestMarshalUnmarshalJSONByStdEncoding(t *testing.T) {
	Base64StdEncoding()
	a := New(1010).Set(10).Set(1001)
	data, err := json.Marshal(a)
	if err != nil {
		t.Errorf(err.Error())
		return
	}

	b := new(BitSet)
	err = json.Unmarshal(data, b)
	if err != nil {
		t.Errorf(err.Error())
		return
	}

	// Bitsets must be equal after marshalling and unmarshalling
	if !a.Equal(b) {
		t.Error("Bitsets are not equal:\n\t", a.DumpAsBits(), "\n\t", b.DumpAsBits())
		return
	}
}

func TestSafeSet(t *testing.T) {
	b := new(BitSet)
	c := b.safeSet()
	outType := fmt.Sprintf("%T", c)
	expType := "[]uint64"
	if outType != expType {
		t.Error("Expecting type: ", expType, ", gotf:", outType)
		return
	}
	if len(c) != 0 {
		t.Error("The slice should be empty")
		return
	}
}

func TestSetBitsetFrom(t *testing.T) {
	u := []uint64{2, 3, 5, 7, 11}
	b := new(BitSet)
	b.SetBitsetFrom(u)
	outType := fmt.Sprintf("%T", b)
	expType := "*bitset.BitSet"
	if outType != expType {
		t.Error("Expecting type: ", expType, ", gotf:", outType)
		return
	}
}

func TestIssue116(t *testing.T) {
	a := []uint64{2, 3, 5, 7, 11}
	b := []uint64{2, 3, 5, 7, 11, 0, 1}
	bitset1 := FromWithLength(320, a)
	bitset2 := FromWithLength(320, b)
	if !bitset1.Equal(bitset2) || !bitset2.Equal(bitset1) {
		t.Error("Bitsets should be equal irrespective of the underlying capacity")
	}
}

func TestFrom(t *testing.T) {
	u := []uint64{2, 3, 5, 7, 11}
	b := From(u)
	outType := fmt.Sprintf("%T", b)
	expType := "*bitset.BitSet"
	if outType != expType {
		t.Error("Expecting type: ", expType, ", gotf:", outType)
		return
	}
}

func TestBytes(t *testing.T) {
	b := new(BitSet)
	c := b.Bytes()
	outType := fmt.Sprintf("%T", c)
	expType := "[]uint64"
	if outType != expType {
		t.Error("Expecting type: ", expType, ", gotf:", outType)
		return
	}
	if len(c) != 0 {
		t.Error("The slice should be empty")
		return
	}
}

func TestCap(t *testing.T) {
	c := Cap()
	if c <= 0 {
		t.Error("The uint capacity should be >= 0")
		return
	}
}

func TestWordsNeededLong(t *testing.T) {
	i := Cap()
	out := wordsNeeded(i)
	if out <= 0 {
		t.Error("Unexpected value: ", out)
		return
	}
}

func TestTestTooLong(t *testing.T) {
	b := new(BitSet)
	if b.Test(1) {
		t.Error("Unexpected value: true")
		return
	}
}

func TestClearTooLong(t *testing.T) {
	b := new(BitSet)
	c := b.Clear(1)
	if b != c {
		t.Error("Unexpected value")
		return
	}
}

func TestClearAll(t *testing.T) {
	u := []uint64{2, 3, 5, 7, 11}
	b := From(u)
	c := b.ClearAll()
	if c.length != 320 {
		t.Error("Unexpected length: ", b.length)
		return
	}
	if c.Test(0) || c.Test(1) || c.Test(2) || c.Test(3) || c.Test(4) || c.Test(5) {
		t.Error("All bits should be unset")
		return
	}
}

func TestRankSelect(t *testing.T) {
	u := []uint{2, 3, 5, 7, 11, 700, 1500}
	b := BitSet{}
	for _, v := range u {
		b.Set(v)
	}

	if b.Rank(5) != 3 {
		t.Error("Unexpected rank")
		return
	}
	if b.Rank(6) != 3 {
		t.Error("Unexpected rank")
		return
	}
	if b.Rank(1500) != 7 {
		t.Error("Unexpected rank")
		return
	}
	if b.Select(0) != 2 {
		t.Error("Unexpected select")
		return
	}
	if b.Select(1) != 3 {
		t.Error("Unexpected select")
		return
	}
	if b.Select(2) != 5 {
		t.Error("Unexpected select")
		return
	}

	if b.Select(5) != 700 {
		t.Error("Unexpected select")
		return
	}
}
func TestFlip(t *testing.T) {
	b := new(BitSet)
	c := b.Flip(11)
	if c.length != 12 {
		t.Error("Unexpected value: ", c.length)
		return
	}
	d := c.Flip(7)
	if d.length != 12 {
		t.Error("Unexpected value: ", d.length)
		return
	}
}

func TestFlipRange(t *testing.T) {
	b := new(BitSet)
	b.Set(1).Set(3).Set(5).Set(7).Set(9).Set(11).Set(13).Set(15)
	c := b.FlipRange(4, 25)
	if c.length != 25 {
		t.Error("Unexpected value: ", c.length)
		return
	}
	d := c.FlipRange(8, 24)
	if d.length != 25 {
		t.Error("Unexpected value: ", d.length)
		return
	}
	//
	for i := uint(0); i < 256; i++ {
		for j := uint(0); j <= i; j++ {
			bits := New(i)
			bits.FlipRange(0, j)
			c := bits.Count()
			if c != j {
				t.Error("Unexpected value: ", c, " expected: ", j)
				return
			}
		}
	}
}

func TestCopy(t *testing.T) {
	a := New(10)
	if a.Copy(nil) != 0 {
		t.Error("No values should be copied")
		return
	}
	a = New(10)
	b := New(20)
	if a.Copy(b) != 10 {
		t.Error("Unexpected value")
		return
	}
}

func TestCopyUnaligned(t *testing.T) {
	a := New(16)
	a.FlipRange(0, 16)
	b := New(1)
	a.Copy(b)
	if b.Count() > b.Len() {
		t.Errorf("targets copied set count (%d) should never be larger than target's length (%d)", b.Count(), b.Len())
	}
	if !b.Test(0) {
		t.Errorf("first bit should still be set in copy: %+v", b)
	}

	// Test a more complex scenario with a mix of bits set in the unaligned space to verify no bits are lost.
	a = New(32)
	a.Set(0).Set(3).Set(4).Set(16).Set(17).Set(29).Set(31)
	b = New(19)
	a.Copy(b)

	const expectedCount = 5
	if b.Count() != expectedCount {
		t.Errorf("targets copied set count: %d, want %d", b.Count(), expectedCount)
	}

	if !(b.Test(0) && b.Test(3) && b.Test(4) && b.Test(16) && b.Test(17)) {
		t.Errorf("expected set bits are not set: %+v", b)
	}
}

func TestCopyFull(t *testing.T) {
	a := New(10)
	b := &BitSet{}
	a.CopyFull(b)
	if b.length != a.length || len(b.set) != len(a.set) {
		t.Error("Expected full length copy")
		return
	}
	for i, v := range a.set {
		if v != b.set[i] {
			t.Error("Unexpected value")
			return
		}
	}
}

func TestNextSetError(t *testing.T) {
	b := new(BitSet)
	c, d := b.NextSet(1)
	if c != 0 || d {
		t.Error("Unexpected values")
		return
	}
}

func TestDeleteWithBitStrings(t *testing.T) {
	type testCase struct {
		input     []string
		deleteIdx uint
		expected  []string
	}

	testCases := []testCase{
		{
			input: []string{
				"1110000000000000000000000000000000000000000000000000000000000001",
			},
			deleteIdx: uint(63),
			expected: []string{
				"0110000000000000000000000000000000000000000000000000000000000001",
			},
		},
		{
			input: []string{
				"1000000000000000000000000000000000000000000000000000000000010101",
			},
			deleteIdx: uint(0),
			expected: []string{
				"0100000000000000000000000000000000000000000000000000000000001010",
			},
		},
		{
			input: []string{
				"0000000000000000000000000000000000000000000000000000000000111000",
			},
			deleteIdx: uint(4),
			expected: []string{
				"0000000000000000000000000000000000000000000000000000000000011000",
			},
		},
		{
			input: []string{
				"1000000000000000000000000000000000000000000000000000000000000001",
				"1010000000000000000000000000000000000000000000000000000000000001",
			},
			deleteIdx: uint(63),
			expected: []string{
				"1000000000000000000000000000000000000000000000000000000000000001",
				"0101000000000000000000000000000000000000000000000000000000000000",
			},
		},
		{
			input: []string{
				"1000000000000000000000000000000000000000000000000000000000000000",
				"1000000000000000000000000000000000000000000000000000000000000001",
				"1000000000000000000000000000000000000000000000000000000000000001",
			},
			deleteIdx: uint(64),
			expected: []string{
				"1000000000000000000000000000000000000000000000000000000000000000",
				"1100000000000000000000000000000000000000000000000000000000000000",
				"0100000000000000000000000000000000000000000000000000000000000000",
			},
		},
		{
			input: []string{
				"0000000000000000000000000000000000000000000000000000000000000001",
				"0000000000000000000000000000000000000000000000000000000000000001",
				"0000000000000000000000000000000000000000000000000000000000000001",
				"0000000000000000000000000000000000000000000000000000000000000001",
				"0000000000000000000000000000000000000000000000000000000000000001",
			},
			deleteIdx: uint(256),
			expected: []string{
				"0000000000000000000000000000000000000000000000000000000000000001",
				"0000000000000000000000000000000000000000000000000000000000000001",
				"0000000000000000000000000000000000000000000000000000000000000001",
				"0000000000000000000000000000000000000000000000000000000000000001",
				"0000000000000000000000000000000000000000000000000000000000000000",
			},
		},
	}

	for _, tc := range testCases {
		var input []uint64
		for _, inputElement := range tc.input {
			parsed, _ := strconv.ParseUint(inputElement, 2, 64)
			input = append(input, parsed)
		}

		var expected []uint64
		for _, expectedElement := range tc.expected {
			parsed, _ := strconv.ParseUint(expectedElement, 2, 64)
			expected = append(expected, parsed)
		}

		b := From(input)
		b.DeleteAt(tc.deleteIdx)
		if len(b.set) != len(expected) {
			t.Errorf("Length of sets expected to be %d, but was %d", len(expected), len(b.set))
			return
		}
		for i := range b.set {
			if b.set[i] != expected[i] {
				t.Errorf("Unexpected output\nExpected: %b\nGot:      %b", expected[i], b.set[i])
				return
			}
		}
	}
}

func TestDeleteWithBitSetInstance(t *testing.T) {
	length := uint(256)
	bitSet := New(length)

	// the indexes that get set in the bit set
	indexesToSet := []uint{0, 1, 126, 127, 128, 129, 170, 171, 200, 201, 202, 203, 255}

	// the position we delete from the bitset
	deleteAt := uint(127)

	// the indexes that we expect to be set after the delete
	expectedToBeSet := []uint{0, 1, 126, 127, 128, 169, 170, 199, 200, 201, 202, 254}

	expected := make(map[uint]struct{})
	for _, index := range expectedToBeSet {
		expected[index] = struct{}{}
	}

	for _, index := range indexesToSet {
		bitSet.Set(index)
	}

	bitSet.DeleteAt(deleteAt)

	for i := uint(0); i < length; i++ {
		if _, ok := expected[i]; ok {
			if !bitSet.Test(i) {
				t.Errorf("Expected index %d to be set, but wasn't", i)
			}
		} else {
			if bitSet.Test(i) {
				t.Errorf("Expected index %d to not be set, but was", i)
			}
		}

	}
}

func TestWriteTo(t *testing.T) {
	const length = 9585
	const oneEvery = 97
	addBuf := []byte(`12345678`)
	bs := New(length)
	// Add some bits
	for i := uint(0); i < length; i += oneEvery {
		bs = bs.Set(i)
	}

	var buf bytes.Buffer
	n, err := bs.WriteTo(&buf)
	if err != nil {
		t.Fatal(err)
	}
	wantSz := buf.Len() // Size of the serialized data in bytes.
	if n != int64(wantSz) {
		t.Errorf("want write size to be %d, got %d", wantSz, n)
	}
	buf.Write(addBuf) // Add additional data on stream.

	// Generate test input for regression tests:
	if false {
		gzout := bytes.NewBuffer(nil)
		gz, err := gzip.NewWriterLevel(gzout, 9)
		if err != nil {
			t.Fatal(err)
		}
		gz.Write(buf.Bytes())
		gz.Close()
		t.Log("Encoded:", base64.StdEncoding.EncodeToString(gzout.Bytes()))
	}

	// Read back.
	bs = New(length)
	n, err = bs.ReadFrom(&buf)
	if err != nil {
		t.Fatal(err)
	}
	if n != int64(wantSz) {
		t.Errorf("want read size to be %d, got %d", wantSz, n)
	}
	// Check bits
	for i := uint(0); i < length; i += oneEvery {
		if !bs.Test(i) {
			t.Errorf("bit %d was not set", i)
		}
	}

	more, err := io.ReadAll(&buf)
	if err != nil {
		t.Fatal(err)
	}
	if !bytes.Equal(more, addBuf) {
		t.Fatalf("extra mismatch. got %v, want %v", more, addBuf)
	}
}

type inCompleteRetBufReader struct {
	returnEvery int64
	reader      io.Reader
	offset      int64
}

func (ir *inCompleteRetBufReader) Read(b []byte) (n int, err error) {
	if ir.returnEvery > 0 {
		maxRead := ir.returnEvery - (ir.offset % ir.returnEvery)
		if len(b) > int(maxRead) {
			b = b[:maxRead]
		}
	}
	n, err = ir.reader.Read(b)
	ir.offset += int64(n)
	return
}

func TestReadFrom(t *testing.T) {
	addBuf := []byte(`12345678`) // Bytes after stream
	tests := []struct {
		length      uint
		oneEvery    uint
		input       string // base64+gzipped
		wantErr     error
		returnEvery int64
	}{
		{
			length:      9585,
			oneEvery:    97,
			input:       "H4sIAAAAAAAC/2IAA9VCCM3AyMDAwMSACVgYGBg4sIgLMDAwKGARd2BgYGjAFB41noDx6IAJajw64IAajw4UoMajg4ZR4/EaP5pQh1g+MDQyNjE1M7cABAAA//9W5OoOwAQAAA==",
			returnEvery: 127,
		},
		{
			length:   1337,
			oneEvery: 42,
			input:    "H4sIAAAAAAAC/2IAA1ZLBgYWEIPRAUQKgJkMcCZYisEBzkSSYkSTYqCxAYZGxiamZuYWgAAAAP//D0wyWbgAAAA=",
		},
		{
			length:   1337, // Truncated input.
			oneEvery: 42,
			input:    "H4sIAAAAAAAC/2IAA9VCCM3AyMDAwARmAQIAAP//vR3xdRkAAAA=",
			wantErr:  io.ErrUnexpectedEOF,
		},
		{
			length:   1337, // Empty input.
			oneEvery: 42,
			input:    "H4sIAAAAAAAC/wEAAP//AAAAAAAAAAA=",
			wantErr:  io.ErrUnexpectedEOF,
		},
	}

	for i, test := range tests {
		t.Run(fmt.Sprint(i), func(t *testing.T) {
			fatalErr := func(err error) {
				t.Helper()
				if err != nil {
					t.Fatal(err)
				}
			}

			var buf bytes.Buffer
			b, err := base64.StdEncoding.DecodeString(test.input)
			fatalErr(err)
			gz, err := gzip.NewReader(bytes.NewBuffer(b))
			fatalErr(err)
			_, err = io.Copy(&buf, gz)
			fatalErr(err)
			fatalErr(gz.Close())

			bs := New(test.length)
			_, err = bs.ReadFrom(&inCompleteRetBufReader{returnEvery: test.returnEvery, reader: &buf})
			if err != nil {
				if errors.Is(err, test.wantErr) {
					// Correct, nothing more we can test.
					return
				}
				t.Fatalf("did not get expected error %v, got %v", test.wantErr, err)
			} else {
				if test.wantErr != nil {
					t.Fatalf("did not get expected error %v", test.wantErr)
				}
			}
			fatalErr(err)

			// Test if correct bits are set.
			for i := uint(0); i < test.length; i++ {
				want := i%test.oneEvery == 0
				got := bs.Test(i)
				if want != got {
					t.Errorf("bit %d was %v, should be %v", i, got, want)
				}
			}

			more, err := io.ReadAll(&buf)
			fatalErr(err)

			if !bytes.Equal(more, addBuf) {
				t.Errorf("extra mismatch. got %v, want %v", more, addBuf)
			}
		})
	}
}

func TestSetAll(t *testing.T) {
	test := func(name string, bs *BitSet, want uint) {
		t.Run(name, func(t *testing.T) {
			bs.SetAll()
			if bs.Count() != want {
				t.Errorf("expected %d bits to be set, got %d", want, bs.Count())
			}
		})
	}

	test("nil", nil, 0)
	for _, length := range []uint{0, 1, 10, 63, 64, 65, 100, 640} {
		test(fmt.Sprintf("length %d", length), New(length), length)
	}
}

func TestShiftLeft(t *testing.T) {
	data := []uint{5, 28, 45, 72, 89}

	test := func(name string, bits uint) {
		t.Run(name, func(t *testing.T) {
			b := New(200)
			for _, i := range data {
				b.Set(i)
			}

			b.ShiftLeft(bits)

			if int(b.Count()) != len(data) {
				t.Error("bad bits count")
			}

			for _, i := range data {
				if !b.Test(i + bits) {
					t.Errorf("bit %v is not set", i+bits)
				}
			}
		})
	}

	test("zero", 0)
	test("no page change", 19)
	test("shift to full page", 38)
	test("full page shift", 64)
	test("no page split", 80)
	test("with page split", 114)
	test("with extension", 242)
}

func TestShiftRight(t *testing.T) {
	data := []uint{5, 28, 45, 72, 89}

	test := func(name string, bits uint) {
		t.Run(name, func(t *testing.T) {
			b := New(200)
			for _, i := range data {
				b.Set(i)
			}

			b.ShiftRight(bits)

			count := 0
			for _, i := range data {
				if i > bits {
					count++

					if !b.Test(i - bits) {
						t.Errorf("bit %v is not set", i-bits)
					}
				}
			}

			if int(b.Count()) != count {
				t.Error("bad bits count")
			}
		})
	}

	test("zero", 0)
	test("no page change", 3)
	test("no page split", 20)
	test("with page split", 40)
	test("full page shift", 64)
	test("with extension", 70)
	test("full shift", 89)
	test("remove all", 242)
}

func TestWord(t *testing.T) {
	data := []uint64{0x0bfd85fc01af96dd, 0x3fe212a7eae11414, 0x7aa412221245dee1, 0x557092c1711306d5}
	testCases := map[string]struct {
		index    uint
		expected uint64
	}{
		"first word": {
			index:    0,
			expected: 0x0bfd85fc01af96dd,
		},
		"third word": {
			index:    128,
			expected: 0x7aa412221245dee1,
		},
		"off the edge": {
			index:    256,
			expected: 0,
		},
		"way off the edge": {
			index:    6346235235,
			expected: 0,
		},
		"split between two words": {
			index:    96,
			expected: 0x1245dee13fe212a7,
		},
		"partly off edge": {
			index:    254,
			expected: 1,
		},
		"skip one nibble": {
			index:    4,
			expected: 0x40bfd85fc01af96d,
		},
		"slightly offset results": {
			index:    65,
			expected: 0x9ff10953f5708a0a,
		},
	}

	for name, testCase := range testCases {
		t.Run(name, func(t *testing.T) {
			bitSet := From(data)
			output := bitSet.GetWord64AtBit(testCase.index)

			if output != testCase.expected {
				t.Errorf("Word should have returned %d for input %d, but returned %d", testCase.expected, testCase.index, output)
			}
		})
	}
}