Yes. A standard sRGB test image can limit what you see when evaluating a wide-gamut printer, so using a wider-gamut test image is reasonable.

Based on the answers, you have two practical options:

1. Use a dedicated gamut test file intended for this purpose, such as the gamut test file from digitaldog.net.
2. Use a visual test image available in a wider space, such as an Adobe RGB test image from colourmanagement.net.

If you specifically want to experiment with your existing sRGB patch file, Photoshop’s Assign Profile can assign a different color space such as ProPhoto RGB. That changes the meaning of the RGB numbers and expands the apparent gamut. This would ruin a normal photographic image, but it can be useful for synthetic color patches.

For judging actual printer/profile behavior, a visual test image in a wide-gamut space is usually more informative than pure bars alone, because it shows how real image content reproduces as well as patches.