Fixed Stats method for Not iterator.

Added unit tests for Not iterator.

graph/iterator/not_iterator_test.go

@@ -0,0 +1,44 @@
+package iterator
+
+import (
+	"reflect"
+	"testing"
+)
+
+func TestNotIteratorBasics(t *testing.T) {
+	allIt := newFixed()
+	allIt.Add(1)
+	allIt.Add(2)
+	allIt.Add(3)
+	allIt.Add(4)
+
+	toComplementIt := newFixed()
+	toComplementIt.Add(2)
+	toComplementIt.Add(4)
+
+	not := NewNot(toComplementIt, allIt)
+
+	if v, _ := not.Size(); v != 2 {
+		t.Errorf("Unexpected iterator size: got:%d, expected: %d", v, 2)
+	}
+
+	expect := []int{1, 3}
+	for i := 0; i < 2; i++ {
+		if got := iterated(not); !reflect.DeepEqual(got, expect) {
+			t.Errorf("Failed to iterate Not correctly on repeat %d: got:%v expected:%v", i, got, expect)
+		}
+		not.Reset()
+	}
+
+	for _, v := range []int{1, 3} {
+		if !not.Contains(v) {
+			t.Errorf("Failed to correctly check %d as true", v)
+		}
+	}
+
+	for _, v := range []int{2, 4} {
+		if not.Contains(v) {
+			t.Errorf("Failed to correctly check %d as false", v)
+		}
+	}
+}