add setup() tests

setup.go

@@ -37,7 +37,7 @@ func setup(c *caddy.Controller) error {
 	client, err := wgctrl.New()
 	if err != nil {
 		return plugin.Error("wgsd",
-			fmt.Errorf("wgsd: error constructing wgctrl client: %v",
+			fmt.Errorf("error constructing wgctrl client: %v",
 				err))
 	}
 

setup_test.go

@@ -0,0 +1,41 @@
+package wgsd
+
+import (
+	"testing"
+
+	"github.com/caddyserver/caddy"
+)
+
+func TestSetup(t *testing.T) {
+	testCases := []struct {
+		name      string
+		input     string
+		expectErr bool
+	}{
+		{
+			"valid input",
+			"wgsd example.com. wg0",
+			false,
+		},
+		{
+			"missing token",
+			"wgsd example.com.",
+			true,
+		},
+		{
+			"too many tokens",
+			"wgsd example.com. wg0 extra",
+			true,
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			c := caddy.NewTestController("dns", tc.input)
+			err := setup(c)
+			if (err != nil) != tc.expectErr {
+				t.Fatalf("expectErr: %v, got err=%v", tc.expectErr, err)
+			}
+		})
+	}
+}