diff --git a/roaring/naive_test.go b/roaring/naive_test.go
index 154d0f8f5..c1accfb5e 100644
--- a/roaring/naive_test.go
+++ b/roaring/naive_test.go
@@ -15,6 +15,7 @@
 package roaring
 
 import (
+	"math/rand"
 	"reflect"
 	"testing"
 )
@@ -110,13 +111,15 @@ func TestUnionSlice(t *testing.T) {
 }
 
 func TestMaxInSlice(t *testing.T) {
+	// arbitrary, we just want to get the same values every time
+	r := rand.New(rand.NewSource(23))
 	a := []uint64{1, 4, 9, 5, 24, 13}
 	v := maxInSlice(a)
 	if uint64(24) != v {
 		t.Fatalf("expected %v, but got %v", uint64(24), v)
 	}
 
-	for i := uint64(1000); i <= uint64(100000); i++ {
+	for i := uint64(1000); i <= uint64(100000); i += uint64(r.Intn(35)) + 1 {
 		a = append(a, i)
 		if v = maxInSlice(a); v != i {
 			t.Fatalf("expected %v, but got %v", i, v)
diff --git a/roaring/roaring_test.go b/roaring/roaring_test.go
index 4f079102a..e31cbf2ee 100644
--- a/roaring/roaring_test.go
+++ b/roaring/roaring_test.go
@@ -866,7 +866,7 @@ func TestBitmap_UnionInPlaceProp(t *testing.T) {
 		seed               = time.Now().UnixNano()
 		source             = rand.NewSource(seed)
 		rng                = rand.New(source)
-		numTests           = 100
+		numTests           = 20
 		maxNumIntsPerBatch = 100
 		maxNumBatches      = 100
 		maxRangePercent    = 2
@@ -1425,10 +1425,10 @@ func TestBitmap_Shift(t *testing.T) {
 }
 
 func TestBitmap_Quick_Array1(t *testing.T)     { testBitmapQuick(t, 1000, 1000, 2000) }
-func TestBitmap_Quick_Array2(t *testing.T)     { testBitmapQuick(t, 10000, 0, 1000) }
-func TestBitmap_Quick_Bitmap1(t *testing.T)    { testBitmapQuick(t, 10000, 0, 10000) }
-func TestBitmap_Quick_Bitmap2(t *testing.T)    { testBitmapQuick(t, 10000, 10000, 20000) }
-func TestBitmap_Quick_LargeValue(t *testing.T) { testBitmapQuick(t, 10000, 0, math.MaxInt64) }
+func TestBitmap_Quick_Array2(t *testing.T)     { testBitmapQuick(t, 1000, 0, 1000) }
+func TestBitmap_Quick_Bitmap1(t *testing.T)    { testBitmapQuick(t, 1000, 0, 10000) }
+func TestBitmap_Quick_Bitmap2(t *testing.T)    { testBitmapQuick(t, 1000, 10000, 20000) }
+func TestBitmap_Quick_LargeValue(t *testing.T) { testBitmapQuick(t, 1000, 0, math.MaxInt64) }
 
 // Ensure a bitmap can perform basic operations on randomly generated values.
 func testBitmapQuick(t *testing.T, n int, min, max uint64) {
@@ -1504,20 +1504,20 @@ func TestBitmap_Marshal_Quick_Array1(t *testing.T) {
 	testBitmapMarshalQuick(t, 1000, 1000, 2000, false)
 }
 func TestBitmap_Marshal_Quick_Array2(t *testing.T) {
-	testBitmapMarshalQuick(t, 10000, 0, 1000, false)
+	testBitmapMarshalQuick(t, 1000, 0, 1000, false)
 }
 func TestBitmap_Marshal_Quick_Bitmap1(t *testing.T) {
-	testBitmapMarshalQuick(t, 10000, 0, 10000, false)
+	testBitmapMarshalQuick(t, 1000, 0, 10000, false)
 }
 func TestBitmap_Marshal_Quick_Bitmap2(t *testing.T) {
-	testBitmapMarshalQuick(t, 10000, 10000, 20000, false)
+	testBitmapMarshalQuick(t, 1000, 10000, 20000, false)
 }
 func TestBitmap_Marshal_Quick_LargeValue(t *testing.T) {
 	testBitmapMarshalQuick(t, 100, 0, math.MaxInt64, false)
 }
 
 func TestBitmap_Marshal_Quick_Bitmap_Sorted(t *testing.T) {
-	testBitmapMarshalQuick(t, 10000, 0, 10000, true)
+	testBitmapMarshalQuick(t, 1000, 0, 10000, true)
 }
 
 // TODO update for RLE