Basic test no. 3 violates good sense.

"input": [
          [['c0', 'p1'], ['p1', 'c2']],
          {'p1': 0}
        ],

A power plant, that can not supply a single city? That does not make sense and conflicts with the task description:

A power plant can supply itself and connected cities with power, but the range is limited.

So each power plant should have range > 0 and that needs to be added to the preconditions.

Anyone else found something? I'd like to collect everything in the first comment, before any changes are applied.