From b5bd8433ccc43854159d78048e63a3abd113d9a9 Mon Sep 17 00:00:00 2001
From: Todd Gruben <tgruben@umbel.com>
Date: Tue, 30 May 2017 13:27:11 -0500
Subject: [PATCH] added empty and equivlence testing

---
 roaring/roaring.go      |  1 -
 roaring/roaring_test.go | 27 +++++++++++++++++++++++++--
 2 files changed, 25 insertions(+), 3 deletions(-)

diff --git a/roaring/roaring.go b/roaring/roaring.go
index 8d477ba10..4a54d3975 100644
--- a/roaring/roaring.go
+++ b/roaring/roaring.go
@@ -1648,7 +1648,6 @@ func xorArrayBitmap(a, b *container) *container {
 		if b.bitmapContains(v) {
 			output.remove(v)
 		} else {
-
 			output.add(v)
 		}
 	}
diff --git a/roaring/roaring_test.go b/roaring/roaring_test.go
index 32492d870..11bab1c78 100644
--- a/roaring/roaring_test.go
+++ b/roaring/roaring_test.go
@@ -137,8 +137,25 @@ func TestBitmap_Xor_ArrayArray(t *testing.T) {
 	if n := result.Count(); n != 2 {
 		t.Fatalf("unexpected n: %d", n)
 	}
+
+	//equivalence array test
+	result = result.Xor(result)
+	if n := result.Count(); n > 0 {
+		t.Fatalf("unexpected n: %d", n)
+	}
+
 }
 
+//empty array test
+func TestBitmap_Xor_Empty(t *testing.T) {
+	bm1 := roaring.NewBitmap(0, 50000, 1000001, 1000002)
+	empty := roaring.NewBitmap()
+	result := bm1.Xor(empty)
+
+	if n := result.Count(); n != 4 {
+		t.Fatalf("unexpected n: %d", n)
+	}
+}
 func TestBitmap_Xor_ArrayBitmap(t *testing.T) {
 	bm0 := roaring.NewBitmap(1, 70, 200, 4097, 4098)
 	bm1 := roaring.NewBitmap()
@@ -150,14 +167,22 @@ func TestBitmap_Xor_ArrayBitmap(t *testing.T) {
 	if n := result.Count(); n != 4999 {
 		t.Fatalf("unexpected n: %d", n)
 	}
+
+	//equivalence bitmap test
+	result = result.Xor(result)
+	if n := result.Count(); n > 0 {
+		t.Fatalf("unexpected n: %d", n)
+	}
 }
 
 func TestBitmap_Xor_BitmapBitmap(t *testing.T) {
 	bm0 := roaring.NewBitmap()
 	bm1 := roaring.NewBitmap()
+
 	for i := uint64(0); i < 10000; i += 2 {
 		bm1.Add(i)
 	}
+
 	for i := uint64(1); i < 10000; i += 2 {
 		bm0.Add(i)
 	}
@@ -168,8 +193,6 @@ func TestBitmap_Xor_BitmapBitmap(t *testing.T) {
 	}
 }
 
-
-
 // Ensure bitmap can return the number of intersecting bits in two bitmaps.
 func TestBitmap_IntersectionCount_ArrayArray(t *testing.T) {
 	bm0 := roaring.NewBitmap(0, 1000001, 1000002, 1000003)