public void TrySerialize_Invalid_Format()
    {
        // arrange
        var type = new FieldSetType();

        // act
        var success = type.TrySerialize(1, out var serialized);

        // assert
        Assert.False(success);
        Assert.Null(serialized);
    }
    public void TrySerialize()
    {
        // arrange
        var type = new FieldSetType();
        SelectionSetNode selectionSet = Syntax.ParseSelectionSet("{ a b c d e(d: $b) }");

        // act
        var success = type.TrySerialize(selectionSet, out var serialized);

        // assert
        Assert.True(success);
        Assert.Equal("a b c d e(d: $b)", serialized);
    }