Feature: Small input images are not enlarged for thumbnails.
  If the input file is smaller than the requested thumb size,
  the biggest XDG size which is bigger than the input file is returned.
  The actual thumb image will have the same dimensions as the input file.

  Remember, the thumb edge sizes for the XDG sizes are:
  *  128 (normal)
  *  256 (large)
  *  512 (x-large)
  * 1024 (xx-large)

  Example:

  Given an input image with a maximum edge length of 200 pixels,
  When we request an x-large thumbnail, the requested thumbnail edge
  length is 512 and therewith greater than the edge length of the input image.

  As a result, AMT will return the smallest XDG size which is bigger than the 
  input image. In this case "large", because "large" has a max. edge length of 256,
  which is still bigger than the edge length of the input file, but there is no smaller
  XDG size which fulfills this criterion.

  Even though the returned thumbnail has XDG size "large", the actual thumbnail image
  has the original dimension of the input file. It's not scaled up.


  The `-F` switch changes this behavior a little.
  With the `-F` switch, the returned XDG size will always be the one requested.
  So, in the above example, AMT will return the path to the x-large thumb.
  However, the dimensions of the thumbnail will still be the same as the dimensions
  of the original file.
  
  The `-F` switch is just for compatibility reasons. In case some client checks the path,
  this will always return a path that matches the requested size.
  However, clients shouldn't mess with the thumbnail logic and just accept the path returned
  by AMT (or any other XDG-thumbnail wrapper).
  _Not_ using `-F` saves unnecessary computation and disk space.


  Scenario Outline: Input smaller than thumb
    Given a JPEG image with edge size <input size> as input
    And no thumbs exist
    When allmytoes is started with arguments <argument>
    Then  the path to the <XDG thumb size> thumb is returned
    And the <XDG thumb size> thumb is a PNG image with max size <thumb pixel size>
    And no thumb exists for sizes other than <XDG thumb size>

    Examples: Small 100px image, without `-F` switch
      | input size | argument | XDG thumb size | thumb pixel size |
      |        100 | -sn      | normal         | 100              |
      |        100 | -sl      | normal         | 100              |
    
    Examples: Medium 500px image, without `-F` switch
      | input size | argument | XDG thumb size | thumb pixel size |
      |        500 | -sn      | normal         | 128              |
      |        500 | -sl      | large          | 256              |
      |        500 | -sx      | x-large        | 500              |
      |        500 | -sxx     | x-large        | 500              |

    Examples: Small 100px image, with `-F` switch
      | input size | argument | XDG thumb size | thumb pixel size |
      |        100 | -Fsn     | normal         | 100              |
      |        100 | -Fsl     | large          | 100              |
    
    Examples: Medium 500px image, with `-F` switch
      | input size | argument | XDG thumb size | thumb pixel size |
      |        500 | -Fsn     | normal         | 128              |
      |        500 | -Fsl     | large          | 256              |
      |        500 | -Fsx     | x-large        | 500              |
      |        500 | -Fsxx    | xx-large       | 500              |


  Scenario: Requested size is not feasible but exists
    Given a JPEG image with edge size 100 as input
    # Which is smaller than any thumb size
    And a thumb for size x-large exists for the input in standard DB
    # Which is way too big; "normal" size would be feasible
    When allmytoes is started with arguments -sx
    # Which is asking for the too big but existing thumb
    Then  the path to the x-large thumb is returned
    And no thumb exists for sizes other than x-large
    And the thumbs have not been changed
  

  Scenario: Requested size does not exist but feasible size does
    Given a JPEG image with edge size 100 as input
    # Which is smaller than any thumb size
    And a thumb for size normal exists for the input in standard DB
    # Which is the feasible size
    When allmytoes is started with arguments -sx
    # Which is asking for a unnecessary big thumb 
    Then  the path to the normal thumb is returned
    And no thumb exists for sizes other than normal
    And the thumbs have not been changed
    # After AMT has not found the requested size, it has checked for the feasible one and returns it