Refactor adding logging flags

cmd/adapter/adapter_test.go

@@ -178,3 +178,34 @@ func TestParseHeaderArgs(t *testing.T) {
 		}
 	}
 }
+
+func TestFlags(t *testing.T) {
+	cmd := &PrometheusAdapter{
+		PrometheusURL: "https://localhost",
+	}
+	cmd.addFlags()
+
+	flags := cmd.FlagSet
+	if flags == nil {
+		t.Fatalf("FlagSet should not be nil")
+	}
+
+	expectedFlags := []struct {
+		flag         string
+		defaultValue string
+	}{
+		{flag: "v", defaultValue: "0"},                              // logging flag (klog)
+		{flag: "prometheus-url", defaultValue: "https://localhost"}, // default is set in cmd
+	}
+
+	for _, e := range expectedFlags {
+		flag := flags.Lookup(e.flag)
+		if flag == nil {
+			t.Errorf("Flag %q expected to be present, was absent", e.flag)
+			continue
+		}
+		if flag.DefValue != e.defaultValue {
+			t.Errorf("Expected default value %q for flag %q, got %q", e.defaultValue, e.flag, flag.DefValue)
+		}
+	}
+}