Implement and test nucypher stake detach-worker

nucypher/cli/stake.py

@@ -78,6 +78,7 @@ def stake(click_config,
         accounts         Show ETH and NU balances for stakeholder's accounts
         sync             Synchronize stake data with on-chain information
         set-worker       Bound a worker to a staker
+        detach-worker    Detach worker currently bound to a staker
         init             Create a new stake
         divide           Create a new stake from part of an existing one
         collect-reward   Withdraw staking reward
@@ -140,13 +141,18 @@ def stake(click_config,
         emitter.echo("OK!", color='green')
         return  # Exit
 
-    elif action == 'set-worker':
+    elif action in ('set-worker', 'detach-worker'):
 
         if not staking_address:
             staking_address = select_stake(stakeholder=STAKEHOLDER, emitter=emitter).owner_address
 
+        if action == 'set-worker':
             if not worker_address:
                 worker_address = click.prompt("Enter worker address", type=EIP55_CHECKSUM_ADDRESS)
+        elif action == 'detach-worker':
+            if worker_address:
+                raise click.BadOptionUsage(message="detach-worker cannot be used together with --worker-address option")
+            worker_address = BlockchainInterface.NULL_ADDRESS
 
         password = None
         if not hw_wallet:

tests/cli/ursula/test_stakeholder_and_ursula.py

@@ -499,3 +499,34 @@ def test_collect_rewards_integration(click_runner,
 
     # The burner wallet has the reward ethers
     assert staker.token_agent.get_balance(address=staker_address)
+
+
+def test_stake_detach_worker(click_runner,
+                             testerchain,
+                             manual_staker,
+                             manual_worker,
+                             stakeholder_configuration_file_location):
+
+    staker = Staker(is_me=True,
+                    checksum_address=manual_staker,
+                    blockchain=testerchain)
+
+    assert staker.worker_address == manual_worker
+
+    init_args = ('stake', 'detach-worker',
+                 '--config-file', stakeholder_configuration_file_location,
+                 '--staking-address', manual_staker,
+                 '--force')
+
+    user_input = f'{INSECURE_DEVELOPMENT_PASSWORD}'
+    result = click_runner.invoke(nucypher_cli,
+                                 init_args,
+                                 input=user_input,
+                                 catch_exceptions=False)
+    assert result.exit_code == 0
+
+    staker = Staker(is_me=True,
+                    checksum_address=manual_staker,
+                    blockchain=testerchain)
+
+    assert not staker.worker_address