diff --git a/internal/parser/parsers_test.go b/internal/parser/parsers_test.go
new file mode 100644
index 0000000..b48f07d
--- /dev/null
+++ b/internal/parser/parsers_test.go
@@ -0,0 +1,79 @@
+package parser
+
+import (
+	"testing"
+
+	"github.com/nalgeon/redka/internal/testx"
+)
+
+func TestFlag(t *testing.T) {
+	tests := []struct {
+		title string
+		name  string
+		args  [][]byte
+		match bool
+		rest  [][]byte
+	}{
+		{
+			title: "flag_flag",
+			name:  "flag",
+			args:  [][]byte{[]byte("flag")},
+			match: true,
+			rest:  [][]byte{},
+		},
+		{
+			title: "flag_notflag",
+			name:  "flag",
+			args:  [][]byte{[]byte("notflag")},
+			match: false,
+			rest:  [][]byte{[]byte("notflag")},
+		},
+		{
+			title: "flag_FLAG",
+			name:  "flag",
+			args:  [][]byte{[]byte("FLAG")},
+			match: true,
+			rest:  [][]byte{},
+		},
+		{
+			title: "FLAG_flag",
+			name:  "FLAG",
+			args:  [][]byte{[]byte("flag")},
+			match: true,
+			rest:  [][]byte{},
+		},
+		{
+			title: "flag_bytes",
+			name:  "flag",
+			args:  [][]byte{{0, 0, 0}},
+			match: false,
+			rest:  [][]byte{{0, 0, 0}},
+		},
+		{
+			title: "flag_empty",
+			name:  "flag",
+			args:  [][]byte{},
+			match: false,
+			rest:  [][]byte{},
+		},
+		{
+			title: "flag_flag_other",
+			name:  "flag",
+			args:  [][]byte{[]byte("flag"), []byte("other")},
+			match: true,
+			rest:  [][]byte{[]byte("other")},
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.title, func(t *testing.T) {
+			var dest bool
+			parser := Flag(test.name, &dest)
+			match, rest, err := parser(test.args)
+			testx.AssertNoErr(t, err)
+			testx.AssertEqual(t, match, test.match)
+			testx.AssertEqual(t, dest, test.match)
+			testx.AssertEqual(t, rest, test.rest)
+		})
+	}
+}