Add unit tests for the device manager functionality

[manojVivek]

[horrificCoder]

@manojVivek Can I work on this?

[manojVivek]

@horrificCoder That would be fantastic!

[ReshadSadik]

Hi, @horrificCoder are you working on this ? If not I would love to pick this up . @manojVivek

[elidakirigo]

hi, Is anyone working on the unit tests? @manojVivek i'd love to contribute

[manojVivek]

@elidakirigo Yes, that would be fantastic, please go ahead and let us know if you have any questions.

[elidakirigo]

@elidakirigo Yes, that would be fantastic, please go ahead and let us know if you have any questions.

thanks

[Ehsanino82]

hello there i make this pr for this issue. i hope this is helpfull
#1004