diff --git a/tests/test_helper.tcl b/tests/test_helper.tcl
index 062c318e5285e63f378964ccb37e3f3d157cf00e..78b979469559e0f2dacb53dd6a313f731f263342 100644
--- a/tests/test_helper.tcl
+++ b/tests/test_helper.tcl
@@ -47,6 +47,7 @@ set ::all_tests {
     unit/obuf-limits
     unit/bitops
     unit/memefficiency
+    unit/hyperloglog
 }
 # Index to the next test to run in the ::all_tests list.
 set ::next_test 0
diff --git a/tests/unit/hyperloglog.tcl b/tests/unit/hyperloglog.tcl
new file mode 100644
index 0000000000000000000000000000000000000000..e241288ddfa22919c17bb319292f34cc9580415a
--- /dev/null
+++ b/tests/unit/hyperloglog.tcl
@@ -0,0 +1,68 @@
+start_server {tags {"hll"}} {
+    test {HyperLogLog self test passes} {
+        catch {r pfselftest} e
+        set e
+    } {OK}
+
+    test {PFADD without arguments creates an HLL value} {
+        r pfadd hll
+        r exists hll
+    } {1}
+
+    test {Approximated cardinality after creation is zero} {
+        r pfcount hll
+    } {0}
+
+    test {PFADD returns 1 when at least 1 reg was modified} {
+        r pfadd hll a b c
+    } {1}
+
+    test {PFADD returns 0 when no reg was modified} {
+        r pfadd hll a b c
+    } {0}
+
+    test {PFADD works with empty string (regression)} {
+        r pfadd hll ""
+    }
+
+    # Note that the self test stresses much better the
+    # cardinality estimation error. We are testing just the
+    # command implementation itself here.
+    test {PFCOUNT returns approximated cardinality of set} {
+        r del hll
+        set res {}
+        r pfadd hll 1 2 3 4 5
+        lappend res [r pfcount hll]
+        # Call it again to test cached value invalidation.
+        r pfadd hll 6 7 8 8 9 10
+        lappend res [r pfcount hll]
+        set res
+    } {5 10}
+
+    test {PFADD, PFCOUNT, PFMERGE type checking works} {
+        r set foo bar
+        catch {r pfadd foo 1} e
+        assert_match {*WRONGTYPE*} $e
+        catch {r pfcount foo} e
+        assert_match {*WRONGTYPE*} $e
+        catch {r pfmerge bar foo} e
+        assert_match {*WRONGTYPE*} $e
+        catch {r pfmerge foo bar} e
+        assert_match {*WRONGTYPE*} $e
+    }
+
+    test {PFMERGE results on the cardinality of union of sets} {
+        r del hll hll1 hll2 hll3
+        r pfadd hll1 a b c
+        r pfadd hll2 b c d
+        r pfadd hll3 c d e
+        r pfmerge hll hll1 hll2 hll3
+        r pfcount hll
+    } {5}
+
+    test {PFGETREG returns the HyperLogLog raw registers} {
+        r del hll
+        r pfadd hll 1 2 3
+        llength [r pfgetreg hll]
+    } {16384}
+}