Use lists for Exec command prefix examples.

README.md

@@ -648,7 +648,7 @@ def test_pebble_exec():
         name='foo',
         execs={
             scenario.Exec(
-                command_prefix=('ls', '-ll'),
+                command_prefix=['ls', '-ll'],
                 return_code=0,
                 stdout=LS_LL,
             ),
@@ -663,7 +663,7 @@ def test_pebble_exec():
         ctx.on.pebble_ready(container),
         state_in,
     )
-    assert state_out.containers["foo"].get_exec(('ls', '-ll')).stdin == "..."
+    assert state_out.containers["foo"].get_exec(['ls', '-ll']).stdin == "..."
 ```
 
 Scenario will attempt to find the right `Exec` object by matching the provided

scenario/state.py

@@ -660,6 +660,13 @@ class Exec(_max_posargs(1)):
     # change ID: used internally to keep track of mocked processes
     _change_id: int = dataclasses.field(default_factory=_generate_new_change_id)
 
+    def __post_init__(self):
+        # The command prefix can be any sequence type, and a list is tidier to
+        # write when there's only one string. However, this object needs to be
+        # hashable, so can't contain a list. We 'freeze' the sequence to a tuple
+        # to support that.
+        object.__setattr__(self, "command_prefix", tuple(self.command_prefix))
+
     def _run(self) -> int:
         return self._change_id
 
@@ -844,9 +851,9 @@ class Container(_max_posargs(1)):
         container = scenario.Container(
             name='foo',
             execs={
-                scenario.Exec(('whoami', ), return_code=0, stdout='ubuntu'),
+                scenario.Exec(['whoami'], return_code=0, stdout='ubuntu'),
                 scenario.Exec(
-                    ('dig', '+short', 'canonical.com'),
+                    ['dig', '+short', 'canonical.com'],
                     return_code=0,
                     stdout='185.125.190.20\\n185.125.190.21',
                 ),

tests/test_consistency_checker.py

@@ -184,7 +184,7 @@ def test_evt_bad_container_name():
 def test_duplicate_execs_in_container():
     container = Container(
         "foo",
-        execs={Exec(("ls", "-l"), return_code=0), Exec(("ls", "-l"), return_code=1)},
+        execs={Exec(["ls", "-l"], return_code=0), Exec(["ls", "-l"], return_code=1)},
     )
     assert_inconsistent(
         State(containers=[container]),

tests/test_e2e/test_pebble.py

@@ -201,7 +201,7 @@ def callback(self: CharmBase):
                 Container(
                     name="foo",
                     can_connect=True,
-                    execs={Exec((cmd,), stdout=out)},
+                    execs={Exec([cmd], stdout=out)},
                 )
             }
         ),
@@ -224,7 +224,7 @@ def _on_ready(self, _):
             proc.wait_output()
 
     ctx = Context(MyCharm, meta={"name": "foo", "containers": {"foo": {}}})
-    exec = Exec((), stdout=LS)
+    exec = Exec([], stdout=LS)
     container = Container(name="foo", can_connect=True, execs={exec})
     state_out = ctx.run(
         ctx.on.pebble_ready(container=container), State(containers={container})
@@ -332,7 +332,7 @@ def test_exec_wait_error(charm_cls):
             Container(
                 name="foo",
                 can_connect=True,
-                execs={Exec(("foo",), stdout="hello pebble", return_code=1)},
+                execs={Exec(["foo"], stdout="hello pebble", return_code=1)},
             )
         }
     )
@@ -352,7 +352,7 @@ def test_exec_wait_output(charm_cls):
             Container(
                 name="foo",
                 can_connect=True,
-                execs={Exec(("foo",), stdout="hello pebble", stderr="oepsie")},
+                execs={Exec(["foo"], stdout="hello pebble", stderr="oepsie")},
             )
         }
     )
@@ -372,7 +372,7 @@ def test_exec_wait_output_error(charm_cls):
             Container(
                 name="foo",
                 can_connect=True,
-                execs={Exec(("foo",), stdout="hello pebble", return_code=1)},
+                execs={Exec(["foo"], stdout="hello pebble", return_code=1)},
             )
         }
     )