}
	if g, w := lf, LevelWarn+3; g != w {
		t.Errorf("got %v, want %v", g, w)
	}
}

func TestLevelVarMarshalText(t *testing.T) {
	var v LevelVar
	v.Set(LevelWarn)
	data, err := v.MarshalText()
	if err != nil {
		t.Fatal(err)
	}
	var v2 LevelVar
	if err := v2.UnmarshalText(data); err != nil {
		t.Fatal(err)
	}
	if g, w := v2.Level(), LevelWarn; g != w {
		t.Errorf("got %s, want %s", g, w)
	}

fixes the handler's minimum level throughout its lifetime.
Setting it to a [LevelVar] allows the level to be varied dynamically.
A LevelVar holds a Level and is safe to read or write from multiple
goroutines.
To vary the level dynamically for an entire program, first initialize
a global LevelVar:

	var programLevel = new(slog.LevelVar) // Info by default

Then use the LevelVar to construct a handler, and make it the default:

		{"(*JSONHandler).WithGroup", Method, 21},
		{"(*Level).UnmarshalJSON", Method, 21},
		{"(*Level).UnmarshalText", Method, 21},
		{"(*LevelVar).Level", Method, 21},
		{"(*LevelVar).MarshalText", Method, 21},
		{"(*LevelVar).Set", Method, 21},
		{"(*LevelVar).String", Method, 21},
		{"(*LevelVar).UnmarshalText", Method, 21},
		{"(*Logger).Debug", Method, 21},
		{"(*Logger).DebugContext", Method, 21},