Add mock test for redis backend

go.mod

@@ -4,6 +4,8 @@ go 1.13
 
 require (
 	github.com/BurntSushi/toml v0.3.1
+	github.com/alicebob/miniredis v2.5.0+incompatible
+	github.com/alicebob/miniredis/v2 v2.13.3 // indirect
 	github.com/anmitsu/go-shlex v0.0.0-20161002113705-648efa622239
 	github.com/boltdb/bolt v1.3.1
 	github.com/codeskyblue/go-sh v0.0.0-20190412065543-76bd3d59ff27
@@ -13,6 +15,7 @@ require (
 	github.com/go-redis/redis v6.15.9+incompatible
 	github.com/go-redis/redis/v8 v8.3.0
 	github.com/golang/protobuf v1.4.2 // indirect
+	github.com/gomodule/redigo v1.8.2 // indirect
 	github.com/google/go-cmp v0.5.2 // indirect
 	github.com/imdario/mergo v0.3.9
 	github.com/pkg/profile v1.4.0