test: refactor plugin to use parameter not envvar

diff --git a/tests/plugins/feature-test.py b/tests/plugins/feature-test.py
index 45900216..37f27fc2 100755
--- a/tests/plugins/feature-test.py
+++ b/tests/plugins/feature-test.py
@@ -1,7 +1,6 @@
 #!/usr/bin/env python3
 
 from pyln.client import Plugin
-import os
 
 # Register a different set feature of feature bits for each location so we can
 # later check that they are being passed correctly.
@@ -15,10 +14,10 @@ plugin = Plugin(
 
 @plugin.init()
 def init(configuration, options, plugin):
-    disable = os.getenv("PLUGIN_DISABLE")
-    if disable:
+    if options.get('disable-on-init'):
         return {'disable': 'init saying disable'}
     return {}
 
 
+plugin.add_option('disable-on-init', False, 'disable plugin on init', opt_type='bool')
 plugin.run()
diff --git a/tests/test_plugin.py b/tests/test_plugin.py
index fa9137e9..a9345140 100644
--- a/tests/test_plugin.py
+++ b/tests/test_plugin.py
@@ -1748,7 +1748,7 @@ def test_plugin_feature_announce(node_factory):
     assert node['features'] == expected_node_features(extra=[203])
 
 
-def test_plugin_feature_remove(node_factory, monkeypatch):
+def test_plugin_feature_remove(node_factory):
     """Check that features registered by plugins get removed if a plugin
     disables itself.
 
@@ -1759,9 +1759,8 @@ def test_plugin_feature_remove(node_factory, monkeypatch):
      - 1 << 205 for bolt11 invoices
     """
 
-    monkeypatch.setenv("PLUGIN_DISABLE", "1")
     plugin = os.path.join(os.path.dirname(__file__), 'plugins/feature-test.py')
-    l1 = node_factory.get_node(options={'plugin': plugin})
+    l1 = node_factory.get_node(options={'plugin': plugin, 'disable-on-init': True})
 
     # Check that we don't include the features set in getmanifest.
     our_feats = l1.rpc.getinfo()["our_features"]