Get-SPFeature -Site <https://mysharepointsite/sites/test>

Get-SPFeature can also be run on web scope (-Web <WebUrl>), farm scope (-Farm) and web application scope (-WebApplication <WebAppUrl>).

Get all orphaned features on a site collection

Another usage of Get-SPFeature can be to find all features that have no scope:

Get-SPFeature -Site <https://mysharepointsite/sites/test> |? { $_.Scope -eq $null )