#682: Ensure that script exists

tests/conftest.py

@@ -53,7 +53,7 @@ def source_root():
 
 
 @pytest.fixture
-def set_shell(monkeypatch, request):
+def set_shell(monkeypatch):
     def _set(cls):
         shell = cls()
         monkeypatch.setattr('thefuck.shells.shell', shell)

tests/entrypoints/test_alias.py

@@ -0,0 +1,30 @@
+from mock import Mock
+import pytest
+from thefuck.entrypoints.alias import _get_alias
+
+
+@pytest.mark.parametrize(
+    'py2, enable_experimental_instant_mode, which, is_instant', [
+        (False, True, True, True),
+        (False, False, True, False),
+        (False, True, False, False),
+        (True, True, True, False),
+        (True, True, False, False),
+        (True, False, True, False)])
+def test_get_alias(monkeypatch, mocker, py2,
+                   enable_experimental_instant_mode,
+                   which, is_instant):
+    monkeypatch.setattr('six.PY2', py2)
+    args = Mock(
+        enable_experimental_instant_mode=enable_experimental_instant_mode,
+        alias='fuck', )
+    mocker.patch('thefuck.entrypoints.alias.which', return_value=which)
+    shell = Mock(app_alias=lambda _: 'app_alias',
+                 instant_mode_alias=lambda _: 'instant_mode_alias')
+    monkeypatch.setattr('thefuck.entrypoints.alias.shell', shell)
+
+    alias = _get_alias(args)
+    if is_instant:
+        assert alias == 'instant_mode_alias'
+    else:
+        assert alias == 'app_alias'

thefuck/entrypoints/alias.py

@@ -1,20 +1,26 @@
 import six
 from ..logs import warn
 from ..shells import shell
+from ..utils import which
 
 
-def print_alias(known_args):
+def _get_alias(known_args):
     if six.PY2:
         warn("The Fuck will drop Python 2 support soon, more details "
              "https://github.com/nvbn/thefuck/issues/685")
 
+    alias = shell.app_alias(known_args.alias)
+
     if known_args.enable_experimental_instant_mode:
         if six.PY2:
-            warn("Instant mode not supported with Python 2")
+            warn("Instant mode requires Python 3")
-            alias = shell.app_alias(known_args.alias)
+        elif not which('script'):
+            warn("Instant mode requires `script` app")
         else:
-            alias = shell.instant_mode_alias(known_args.alias)
+            return shell.instant_mode_alias(known_args.alias)
-    else:
-        alias = shell.app_alias(known_args.alias)
 
-    print(alias)
+    return alias
+
+
+def print_alias(known_args):
+    print(_get_alias(known_args))