Fail early when invalid port is configured

internal/main.go

@@ -135,7 +135,9 @@ func getKubedockURL() (string, error) {
 	}
 
 	port := strings.Split(viper.GetString("server.listen-addr")+":", ":")[1]
-	klog.Infof("api server started listening on %s", port)
+	if port == "" {
+		return "", fmt.Errorf("expected a port to be configured for listen-addr")
+	}
 
 	proto := "http"
 	if viper.GetBool("server.tls-enable") {

internal/main_test.go

@@ -0,0 +1,39 @@
+package internal
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/joyrex2001/kubedock/internal/util/myip"
+	"github.com/spf13/viper"
+)
+
+func TestGetKubedockURL(t *testing.T) {
+	tests := []struct {
+		listen string
+		tls    bool
+		res    string
+		suc    bool
+	}{
+		{":1234", false, "http://{{IP}}:1234", true},
+		{":1234", true, "https://{{IP}}:1234", true},
+		{"1234", false, "", false},
+	}
+
+	ip, _ := myip.Get()
+	for i, tst := range tests {
+		viper.Set("server.listen-addr", tst.listen)
+		viper.Set("server.tls-enable", tst.tls)
+		res, err := getKubedockURL()
+		if tst.suc && err != nil {
+			t.Errorf("failed test %d - unexpected error %s", i, err)
+		}
+		if !tst.suc && err == nil {
+			t.Errorf("failed test %d - expected error, but succeeded instead", i)
+		}
+		tst.res = strings.ReplaceAll(tst.res, "{{IP}}", ip)
+		if err == nil && res != tst.res {
+			t.Errorf("failed test %d - expected %s, but got %s", i, tst.res, res)
+		}
+	}
+}