diff --git a/buzhash_test.go b/buzhash_test.go
index 931f23574f0aff470e1ddb04278c1a1af33df4e1..05ad7c380fec042c2a10a19a18293c868e8dcf73 100644
--- a/buzhash_test.go
+++ b/buzhash_test.go
@@ -9,7 +9,13 @@ import (
 )
 
 func testBuzhashChunking(t *testing.T, buf []byte) (chunkCount int) {
-	util.NewTimeSeededRand().Read(buf)
+	n, err := util.NewTimeSeededRand().Read(buf)
+	if n < len(buf) {
+		t.Fatalf("expected %d bytes, got %d", len(buf), n)
+	}
+	if err != nil {
+		t.Fatal(err)
+	}
 
 	r := NewBuzhash(bytes.NewReader(buf))
 
diff --git a/rabin_test.go b/rabin_test.go
index 857e97c2ca1ef528d75ed69970e1b73449feb2ba..2e19a82c74b25c5b0f38d329f11ce31f5822bc37 100644
--- a/rabin_test.go
+++ b/rabin_test.go
@@ -12,7 +12,13 @@ import (
 
 func TestRabinChunking(t *testing.T) {
 	data := make([]byte, 1024*1024*16)
-	util.NewTimeSeededRand().Read(data)
+	n, err := util.NewTimeSeededRand().Read(data)
+	if n < len(data) {
+		t.Fatalf("expected %d bytes, got %d", len(data), n)
+	}
+	if err != nil {
+		t.Fatal(err)
+	}
 
 	r := NewRabin(bytes.NewReader(data), 1024*256)
 
@@ -62,7 +68,13 @@ func chunkData(t *testing.T, newC newSplitter, data []byte) map[string]blocks.Bl
 
 func testReuse(t *testing.T, cr newSplitter) {
 	data := make([]byte, 1024*1024*16)
-	util.NewTimeSeededRand().Read(data)
+	n, err := util.NewTimeSeededRand().Read(data)
+	if n < len(data) {
+		t.Fatalf("expected %d bytes, got %d", len(data), n)
+	}
+	if err != nil {
+		t.Fatal(err)
+	}
 
 	ch1 := chunkData(t, cr, data[1000:])
 	ch2 := chunkData(t, cr, data)