diff --git a/roaring/internal_test.go b/roaring/internal_test.go
deleted file mode 100644
index 107851489..000000000
--- a/roaring/internal_test.go
+++ /dev/null
@@ -1,57 +0,0 @@
-// Copyright 2017 Pilosa Corp.
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-//     http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-package roaring
-
-import (
-	"reflect"
-	"testing"
-)
-
-// Ensure iterator returns values from a bitmap.
-func TestBitmapIterator(t *testing.T) {
-	for i, tt := range []struct {
-		bitmap []uint64
-		values []uint16
-	}{
-		// Empty
-		{
-			bitmap: []uint64{6}, // 0110
-			values: []uint16{1, 2},
-		},
-
-		// Single uint64 bitmap
-		{
-			bitmap: []uint64{6}, // 0110
-			values: []uint16{1, 2},
-		},
-
-		// Multi uint64 bitmap
-		{
-			bitmap: []uint64{1 << 63, 1, 0, 1, 3 << 62},
-			values: []uint16{63, 64, 192, 318, 319},
-		},
-	} {
-		itr := newBitmapIterator(tt.bitmap)
-
-		var a []uint16
-		for v, eof := itr.next(); !eof; v, eof = itr.next() {
-			a = append(a, v)
-		}
-
-		if !reflect.DeepEqual(a, tt.values) {
-			t.Errorf("%d. unexpected values: exp=%+v, got=%+v", i, a, tt.values)
-		}
-	}
-}
diff --git a/roaring/roaring.go b/roaring/roaring.go
index 5a8c59cd1..30a5eeea3 100644
--- a/roaring/roaring.go
+++ b/roaring/roaring.go
@@ -718,18 +718,18 @@ func (b *Bitmap) UnmarshalBinary(data []byte) error {
 		}
 
 		// Unmarshal the op and apply it.
-		var op op
-		if err := op.UnmarshalBinary(buf); err != nil {
+		var opr op
+		if err := opr.UnmarshalBinary(buf); err != nil {
 			// FIXME(benbjohnson): return error with position so file can be trimmed.
 			return err
 		}
-		op.apply(b)
+		opr.apply(b)
 
 		// Increase the op count.
 		b.opN++
 
 		// Move the buffer forward.
-		buf = buf[op.size():]
+		buf = buf[opr.size():]
 	}
 
 	return nil
@@ -2990,38 +2990,6 @@ func popcount(x uint64) (n uint64) {
 	return x >> 56
 }
 
-// bitmapIterator represents an iterator over container bitmap values.
-type bitmapIterator struct {
-	bitmap []uint64
-	i      int
-}
-
-// Returns eof as true if there are no values left in the iterator.
-func (itr *bitmapIterator) next() (v uint16, eof bool) {
-	if itr.i+1 >= len(itr.bitmap)*64 {
-		return 0, true
-	}
-	itr.i++
-
-	// Find first non-zero bit in current bitmap, if possible.
-	hb := itr.i >> 6
-	lb := itr.bitmap[hb] >> (uint(itr.i) % 64)
-	if lb != 0 {
-		itr.i = itr.i + trailingZeroN(lb)
-		return uint16(itr.i), false
-	}
-
-	// Otherwise iterate through remaining bitmaps to find next bit.
-	for hb++; hb < len(itr.bitmap); hb++ {
-		if itr.bitmap[hb] != 0 {
-			itr.i = hb<<6 + trailingZeroN(itr.bitmap[hb])
-			return uint16(itr.i), false
-		}
-	}
-
-	return 0, true
-}
-
 // ErrorList represents a list of errors.
 type ErrorList []error
 
@@ -3057,13 +3025,6 @@ func (a *ErrorList) AppendWithPrefix(err error, prefix string) {
 	}
 }
 
-// assert panics with a formatted message if condition is false.
-func assert(condition bool, format string, a ...interface{}) {
-	if !condition {
-		panic(fmt.Sprintf(format, a...))
-	}
-}
-
 // xorArrayRun computes the exclusive or of an array and a run container.
 func xorArrayRun(a, b *container) *container {
 	output := &container{containerType: ContainerRun}
diff --git a/roaring/roaring_internal_test.go b/roaring/roaring_internal_test.go
index e333ca513..28b398c96 100644
--- a/roaring/roaring_internal_test.go
+++ b/roaring/roaring_internal_test.go
@@ -2493,65 +2493,6 @@ func TestBitmap_BitmapWriteToWithEmpty(t *testing.T) {
 	}
 }
 
-func Test_BufBitmapIterator_Next(t *testing.T) {
-	b := NewBitmap()
-	for i := uint64(0); i < 4097; i++ {
-		b.Add(i)
-	}
-	if !b.containers[0].isBitmap() {
-		t.Fatalf("wrong container type")
-	}
-
-	bin := []uint16{}
-
-	itr := newBufBitmapIterator(newBitmapIterator(b.containers[0].bitmap))
-	x := uint16(0)
-
-	for i := 0; i < 10; i++ {
-		x, _ = itr.next()
-		bin = append(bin, x)
-	}
-	exp := []uint16{0, 1, 2, 3, 4, 5, 6, 7, 8, 9}
-	if !reflect.DeepEqual(bin, exp) {
-		t.Fatalf("BufBitmapIterator expected (%v) but got (%v)", exp, bin)
-	}
-
-	// ensure that unread points next back one such that the last value is repeated
-	itr.unread()
-	x, _ = itr.next()
-	bin = append(bin, x)
-	exp = append(exp, uint16(9))
-	if !reflect.DeepEqual(bin, exp) {
-		t.Fatalf("BufBitmapIterator expected (%v) but got (%v)", exp, bin)
-	}
-}
-
-func Test_BufBitmapIterator_UnreadPanic(t *testing.T) {
-
-	defer func() {
-		if r := recover(); r == nil {
-			t.Errorf("BufBitmapIterator unread did not panic")
-		}
-	}()
-
-	b := NewBitmap()
-	for i := uint64(0); i < 4097; i++ {
-		b.Add(i)
-	}
-	if !b.containers[0].isBitmap() {
-		t.Fatalf("wrong container type")
-	}
-
-	itr := newBufBitmapIterator(newBitmapIterator(b.containers[0].bitmap))
-	for i := 0; i < 10; i++ {
-		itr.next()
-	}
-
-	// ensure that unreading back-to-back panics
-	itr.unread()
-	itr.unread()
-}
-
 func TestSearch64(t *testing.T) {
 	tests := []struct {
 		a     []uint64