public void Match()
    {
        // Given
        var expression = new RepExpression(new TextExpression("x"), null, new RepCount(0, -1));

        // When
        var result = expression.Transform("xxxx");

        // Then
        Assert.Equal("xxxx", result);
    }
    public void Separator()
    {
        // Given
        var expression = new RepExpression(new TextExpression("x"), new TextExpression("y"), new RepCount(0, -1));

        // When
        var result = expression.Transform("xyxyxyx");

        // Then
        Assert.Equal("xyxyxyx", result);
    }