cat: extract parameter validation and add a test

cmd/restic/cmd_cat.go

@@ -13,8 +13,6 @@ import (
 	"github.com/restic/restic/internal/restic"
 )
 
-var allowedCmds = []string{"config", "index", "snapshot", "key", "masterkey", "lock", "pack", "blob", "tree"}
-
 var cmdCat = &cobra.Command{
 	Use:   "cat [flags] [masterkey|config|pack ID|blob ID|snapshot ID|index ID|key ID|lock ID|tree snapshot:subfolder]",
 	Short: "Print internal objects to stdout",
@@ -36,21 +34,21 @@ func init() {
 	cmdRoot.AddCommand(cmdCat)
 }
 
-func validateParam(param string) bool {
-	for _, v := range allowedCmds {
-		if v == param {
-			return true
-		}
-	}
-	return false
-}
+func validateCatArgs(args []string) error {
+	var allowedCmds = []string{"config", "index", "snapshot", "key", "masterkey", "lock", "pack", "blob", "tree"}
 
-func runCat(ctx context.Context, gopts GlobalOptions, args []string) error {
 	if len(args) < 1 {
 		return errors.Fatal("type not specified")
 	}
 
-	if ok := validateParam(args[0]); !ok {
+	validType := false
+	for _, v := range allowedCmds {
+		if v == args[0] {
+			validType = true
+			break
+		}
+	}
+	if !validType {
 		return errors.Fatalf("invalid type %q, must be one of [%s]", args[0], strings.Join(allowedCmds, "|"))
 	}
 
@@ -58,6 +56,14 @@ func runCat(ctx context.Context, gopts GlobalOptions, args []string) error {
 		return errors.Fatal("ID not specified")
 	}
 
+	return nil
+}
+
+func runCat(ctx context.Context, gopts GlobalOptions, args []string) error {
+	if err := validateCatArgs(args); err != nil {
+		return err
+	}
+
 	repo, err := OpenRepository(ctx, gopts)
 	if err != nil {
 		return err

cmd/restic/cmd_cat_test.go

@@ -0,0 +1,30 @@
+package main
+
+import (
+	"strings"
+	"testing"
+
+	rtest "github.com/restic/restic/internal/test"
+)
+
+func TestCatArgsValidation(t *testing.T) {
+	for _, test := range []struct {
+		args []string
+		err  string
+	}{
+		{[]string{}, "Fatal: type not specified"},
+		{[]string{"masterkey"}, ""},
+		{[]string{"invalid"}, `Fatal: invalid type "invalid"`},
+		{[]string{"snapshot"}, "Fatal: ID not specified"},
+		{[]string{"snapshot", "12345678"}, ""},
+	} {
+		t.Run("", func(t *testing.T) {
+			err := validateCatArgs(test.args)
+			if test.err == "" {
+				rtest.Assert(t, err == nil, "unexpected error %q", err)
+			} else {
+				rtest.Assert(t, strings.Contains(err.Error(), test.err), "unexpected error expected %q to contain %q", err, test.err)
+			}
+		})
+	}
+}