fix: utils tests on macOS

test_utils tests were failing on macOS when the settings file was properly
defined and present.

Close #560.

tests/test_utils.py

@@ -4,7 +4,7 @@ import sys
 import tempfile
 import unittest
 from io import StringIO
-from unittest.mock import MagicMock, patch
+from unittest.mock import MagicMock, mock_open, patch
 
 from tutor import exceptions, utils
 
@@ -152,9 +152,59 @@ class UtilsTests(unittest.TestCase):
         process.kill.assert_called_once()
 
     @patch("sys.platform", "win32")
-    def test_check_macos_memory_win32_should_skip(self) -> None:
-        utils.check_macos_memory()
+    def test_check_macos_docker_memory_win32_should_skip(self) -> None:
+        utils.check_macos_docker_memory()
 
     @patch("sys.platform", "darwin")
-    def test_check_macos_memory_darwin_filenotfound(self) -> None:
-        self.assertRaises(exceptions.TutorError, utils.check_macos_memory)
+    def test_check_macos_docker_memory_darwin(self) -> None:
+        with patch("tutor.utils.open", mock_open(read_data='{"memoryMiB": 4096}')):
+            utils.check_macos_docker_memory()
+
+    @patch("sys.platform", "darwin")
+    def test_check_macos_docker_memory_darwin_filenotfound(self) -> None:
+        with patch("tutor.utils.open", mock_open()) as mock_open_settings:
+            mock_open_settings.return_value.__enter__.side_effect = FileNotFoundError
+            with self.assertRaises(exceptions.TutorError) as e:
+                utils.check_macos_docker_memory()
+            self.assertIn("Error accessing Docker settings file", e.exception.args[0])
+
+    @patch("sys.platform", "darwin")
+    def test_check_macos_docker_memory_darwin_json_decode_error(self) -> None:
+        with patch("tutor.utils.open", mock_open(read_data="invalid")):
+            with self.assertRaises(exceptions.TutorError) as e:
+                utils.check_macos_docker_memory()
+            self.assertIn("invalid JSON", e.exception.args[0])
+
+    @patch("sys.platform", "darwin")
+    def test_check_macos_docker_memory_darwin_key_error(self) -> None:
+        with patch("tutor.utils.open", mock_open(read_data="{}")):
+            with self.assertRaises(exceptions.TutorError) as e:
+                utils.check_macos_docker_memory()
+            self.assertIn("key 'memoryMiB' not found", e.exception.args[0])
+
+    @patch("sys.platform", "darwin")
+    def test_check_macos_docker_memory_darwin_type_error(self) -> None:
+        with patch(
+            "tutor.utils.open", mock_open(read_data='{"memoryMiB": "invalidstring"}')
+        ):
+            with self.assertRaises(exceptions.TutorError) as e:
+                utils.check_macos_docker_memory()
+            self.assertIn("Unexpected JSON data", e.exception.args[0])
+
+    @patch("sys.platform", "darwin")
+    def test_check_macos_docker_memory_darwin_insufficient_memory(self) -> None:
+        with patch("tutor.utils.open", mock_open(read_data='{"memoryMiB": 4095}')):
+            with self.assertRaises(exceptions.TutorError) as e:
+                utils.check_macos_docker_memory()
+            self.assertEqual(
+                "Docker is configured to allocate 4095 MiB RAM, less than the recommended 4096 MiB",
+                e.exception.args[0],
+            )
+
+    @patch("sys.platform", "darwin")
+    def test_check_macos_docker_memory_darwin_encoding_error(self) -> None:
+        with patch("tutor.utils.open", mock_open()) as mock_open_settings:
+            mock_open_settings.return_value.__enter__.side_effect = TypeError
+            with self.assertRaises(exceptions.TutorError) as e:
+                utils.check_macos_docker_memory()
+            self.assertIn("Text encoding error", e.exception.args[0])

tutor/commands/local.py

@@ -45,16 +45,14 @@ def local(context: click.Context) -> None:
 @click.pass_context
 def quickstart(context: click.Context, non_interactive: bool, pullimages: bool) -> None:
     try:
-        utils.check_macos_memory()
+        utils.check_macos_docker_memory()
     except exceptions.TutorError as e:
         fmt.echo_alert(
-            """Could not verify sufficient RAM allocation in Docker:
-    {}
-Tutor may not work if Docker is configured with < 4 GB RAM. Please follow instructions from:
+            f"""Could not verify sufficient RAM allocation in Docker:
+    {e}
+Tutor may not work if Docker is configured with < 4 GB RAM. Please follow the instructions from:
     https://docs.tutor.overhang.io/install.html
-            """.format(
-                str(e)
-            )
+            """
         )
 
     if tutor_env.needs_major_upgrade(context.obj.root):

tutor/utils.py

@@ -222,9 +222,12 @@ def check_output(*command: str) -> bytes:
         ) from e
 
 
-def check_macos_memory() -> None:
+def check_macos_docker_memory() -> None:
     """
     Try to check that the RAM allocated to the Docker VM on macOS is at least 4 GB.
+
+    Parse macOS Docker settings file from user directory and return the max
+    allocated memory. Will raise TutorError in case of parsing/loading error.
     """
     if sys.platform != "darwin":
         return
@@ -238,27 +241,25 @@ def check_macos_memory() -> None:
             data = json.load(fp)
             memory_mib = int(data["memoryMiB"])
     except OSError as e:
-        raise exceptions.TutorError(
-            "Error accessing {}: [{}] {}".format(settings_path, e.errno, e.strerror)
-        ) from e
+        raise exceptions.TutorError(f"Error accessing Docker settings file: {e}") from e
     except json.JSONDecodeError as e:
         raise exceptions.TutorError(
-            "Error reading {}: invalid JSON: {} [{}:{}]".format(
-                settings_path, e.msg, e.lineno, e.colno
-            )
+            f"Error reading {settings_path}, invalid JSON: {e}"
         ) from e
-    except (ValueError, TypeError, OverflowError) as e:
-        # ValueError from open() indicates an encoding error
+    except ValueError as e:
         raise exceptions.TutorError(
-            "Text encoding error or unexpected JSON data: in {}: {}".format(
-                settings_path, str(e)
-            )
+            f"Unexpected JSON data in {settings_path}: {e}"
         ) from e
     except KeyError as e:
         # Value is absent (Docker creates the file with the default setting of 2048 explicitly
         # written in, so we shouldn't need to assume a default value here.)
         raise exceptions.TutorError(
-            "key 'memoryMiB' not found in {}".format(settings_path)
+            f"key 'memoryMiB' not found in {settings_path}"
+        ) from e
+    except (TypeError, OverflowError) as e:
+        # TypeError from open() indicates an encoding error
+        raise exceptions.TutorError(
+            f"Text encoding error in {settings_path}: {e}"
         ) from e
 
     if memory_mib < 4096: