diff --git a/tests/unit/type/zset.tcl b/tests/unit/type/zset.tcl
index 238eebb9d..d33b4bb35 100644
--- a/tests/unit/type/zset.tcl
+++ b/tests/unit/type/zset.tcl
@@ -43,6 +43,63 @@ start_server {tags {"zset"}} {
             assert_error "*not*float*" {r zadd myzset nan abc}
         }
 
+        test "ZADD with options syntax error with incomplete pair" {
+            r del ztmp
+            catch {r zadd ztmp xx 10 x 20} err
+            set err
+        } {ERR*}
+
+        test "ZADD XX option without key - $encoding" {
+            r del ztmp
+            assert {[r zadd ztmp xx 10 x] == 0}
+            assert {[r type ztmp] eq {none}}
+        }
+
+        test "ZADD XX existing key - $encoding" {
+            r del ztmp
+            r zadd ztmp 10 x
+            assert {[r zadd ztmp xx 20 y] == 0}
+            assert {[r zcard ztmp] == 1}
+        }
+
+        test "ZADD XX returns the number of elements actually added" {
+            r del ztmp
+            r zadd ztmp 10 x
+            set retval [r zadd ztmp 10 x 20 y 30 z]
+            assert {$retval == 2}
+        }
+
+        test "ZADD XX updates existing elements score" {
+            r del ztmp
+            r zadd ztmp 10 x 20 y 30 z
+            r zadd ztmp xx 5 foo 11 x 21 y 40 zap
+            assert {[r zcard ztmp] == 3}
+            assert {[r zscore ztmp x] == 11}
+            assert {[r zscore ztmp y] == 21}
+        }
+
+        test "ZADD XX and NX are not compatible" {
+            r del ztmp
+            catch {r zadd ztmp xx nx 10 x} err
+            set err
+        } {ERR*}
+
+        test "ZADD NX with non exisitng key" {
+            r del ztmp
+            r zadd ztmp nx 10 x 20 y 30 z
+            assert {[r zcard ztmp] == 3}
+        }
+
+        test "ZADD NX only add new elements without updating old ones" {
+            r del ztmp
+            r zadd ztmp 10 x 20 y 30 z
+            assert {[r zadd ztmp nx 11 x 21 y 100 a 200 b] == 2}
+            assert {[r zscore ztmp x] == 10}
+            assert {[r zscore ztmp y] == 20}
+            assert {[r zscore ztmp a] == 100}
+            assert {[r zscore ztmp b] == 200}
+        }
+
         test "ZINCRBY calls leading to NaN result in error" {
             r zincrby myzset +inf abc
             assert_error "*NaN*" {r zincrby myzset -inf abc}
@@ -77,6 +134,8 @@ start_server {tags {"zset"}} {
         }
 
         test "ZCARD basics - $encoding" {
+            r del ztmp
+            r zadd ztmp 10 a 20 b 30 c
             assert_equal 3 [r zcard ztmp]
             assert_equal 0 [r zcard zdoesntexist]
         }