Since this has been down-sampled to a 300ppi file, I agree. The original 360ppi file, or a vector art file would have more value. Line tests are fun but photographic detail tests can be more revealing and channeling for a printer's masking/screening algorithms. Would love to hear from anyone who has something really good for this.
To check what inkload a paper can have (media preset) you could use one of the greyscale stepwedges I made. Have to add more resolution choices one day. Look for the bleed on the contrasty lines and between the greyscale patches that are close to one another. Measure the Dmax on the shadow patches to see whether the density runs back and a media preset with less ink can be used. With that done you can make a resolution test.
There's nothing wrong with the ddisoftware targets and using the method described in the manual to see what the driver, the media preset, the quality settings and the printer do with the selected paper. With the right native resolution already fixed in the target no other up or downsampling happens and the application you print from should have no influence if no special settings like print sharpening are set.
A step further is to look what the downsampling does by selecting a media preset and quality settings that ask for 300 PPI native resolution input and checking the 600 PPI target results (Canon + HP, 360-720 for the Epson). Tells you whether the driver-firmware of the printer has any anti-aliasing algorithms aboard for downsampling. You can also change the target in Photoshop by making the size half and start from 1200 PPI to check the downsampling to 600 PPI. No extrapolation happens on the target in PS so the data isn't corrupted that way. It will show you that driver designers can still learn something from specific application implants like Qimage's variable anti-aliasing on downsampling.
When you know the true optical resolution of that paper and the suitable media preset of the printer system you also know what data you could send to that combination. That doesn't have to be the native resolution of the media preset + one of its quality settings but with any file that isn't at the native resolution of that combination there will be up or downsampling done by the driver or by the application. That's the way drivers work, they have a set of 2-4 input resolutions to start with to keep the computing to print resolutions DPI easier. Like Qimage the HP Z3100 driver shows the native resolution when you go into the custom quality settings for a given media preset, it's called render DPI there, PPI would be the better abbreviation. Much depends on the quality of the up and downsampling routines in the driver or the application whether the resolution you send to it will be kept at the same quality level till the printer squirts droplets on the paper. As it is far easier to archive one image file only at the best optical resolution quality possible with your equipment it is also easier to use that file for any size you want to print and avoid any editing on that file per printsize choice. Qimage does that for you in an easy way. It allows you to throw any file resolution in the print queue and print to any size you want with the best extrapolation, anti-aliasing, smart sharpening algorithms available. Meanwhile the test above told you what the paper actually can deliver so checking the input resolution in the print queue and the active printer native resolution in the preview window of Qimage should make clear what you may expect in the print. A heavy upsampled image doesn't print better at a 4 times higher native resolution than one that already is higher than the input resolution. Or you must have a printer that can only print without banding at the highest settings which is a problem that should be solved first. You can also check at what size the image will meet the paper quality and decide what media preset quality to use, either up or downsample then. You could decide to select a print size that matches the input resolution with the native resolution of the selected media preset quality and avoid any extrapolation from camera to print. It is flexible and at the same time transparent on what is done with your image.