test: add type hinting to test_helpers (#1014)

* Add type hints to tests/test_helpers
* For fake_script and fake_script_calls, there are a bunch of `type: ignore`s to work around not being able to state the type of `fake_script_path` - I think there will be a few of these through other test modules as well, as hints are added there. I feel it would be cleaner to have the fake script functionality in a class rather than dynamically added to TestCase instances, but [that is a much more substantial change](tonyandrewmeyer@46238ee)

Partially addresses #1007

pyproject.toml

@@ -33,6 +33,7 @@ include = ["ops/*.py", "ops/_private/*.py",
     "test/test_infra.py",
     "test/test_jujuversion.py",
     "test/test_log.py",
+    "test/test_helpers.py",
     "test/test_lib.py",
 ]
 pythonVersion = "3.8" # check no python > 3.8 features are used

test/test_helpers.py

@@ -17,14 +17,15 @@
 import shutil
 import subprocess
 import tempfile
+import typing
 import unittest
 
 import ops
 from ops.model import _ModelBackend
 from ops.storage import SQLiteStorage
 
 
-def fake_script(test_case, name, content):
+def fake_script(test_case: unittest.TestCase, name: str, content: str):
     if not hasattr(test_case, 'fake_script_path'):
         fake_script_path = tempfile.mkdtemp('-fake_script')
         old_path = os.environ["PATH"]
@@ -35,40 +36,42 @@ def cleanup():
             os.environ['PATH'] = old_path
 
         test_case.addCleanup(cleanup)
-        test_case.fake_script_path = pathlib.Path(fake_script_path)
+        test_case.fake_script_path = pathlib.Path(fake_script_path)  # type: ignore
 
-    template_args = {
+    template_args: typing.Dict[str, str] = {
         'name': name,
-        'path': test_case.fake_script_path.as_posix(),
+        'path': test_case.fake_script_path.as_posix(),  # type: ignore
         'content': content,
     }
 
-    path = test_case.fake_script_path / name
-    with path.open('wt') as f:
+    path: pathlib.Path = test_case.fake_script_path / name  # type: ignore
+    with path.open('wt') as f:  # type: ignore
         # Before executing the provided script, dump the provided arguments in calls.txt.
         # ASCII 1E is RS 'record separator', and 1C is FS 'file separator', which seem appropriate.
-        f.write('''#!/bin/sh
+        f.write(  # type: ignore
+            '''#!/bin/sh
 {{ printf {name}; printf "\\036%s" "$@"; printf "\\034"; }} >> {path}/calls.txt
 {content}'''.format_map(template_args))
-    os.chmod(str(path), 0o755)
+    os.chmod(str(path), 0o755)  # type: ignore
     # TODO: this hardcodes the path to bash.exe, which works for now but might
     #       need to be set via environ or something like that.
-    path.with_suffix(".bat").write_text(
+    path.with_suffix(".bat").write_text(  # type: ignore
         f'@"C:\\Program Files\\git\\bin\\bash.exe" {path} %*\n')
 
 
-def fake_script_calls(test_case, clear=False):
-    calls_file = test_case.fake_script_path / 'calls.txt'
-    if not calls_file.exists():
+def fake_script_calls(test_case: unittest.TestCase,
+                      clear: bool = False) -> typing.List[typing.List[str]]:
+    calls_file: pathlib.Path = test_case.fake_script_path / 'calls.txt'  # type: ignore
+    if not calls_file.exists():  # type: ignore
         return []
 
     # newline and encoding forced to linuxy defaults because on
     # windows they're written from git-bash
-    with calls_file.open('r+t', newline='\n', encoding='utf8') as f:
-        calls = [line.split('\x1e') for line in f.read().split('\x1c')[:-1]]
+    with calls_file.open('r+t', newline='\n', encoding='utf8') as f:  # type: ignore
+        calls = [line.split('\x1e') for line in f.read().split('\x1c')[:-1]]  # type: ignore
         if clear:
-            f.truncate(0)
-    return calls
+            f.truncate(0)  # type: ignore
+    return calls  # type: ignore
 
 
 class FakeScriptTest(unittest.TestCase):
@@ -105,7 +108,10 @@ def test_fake_script_clear(self):
 
 class BaseTestCase(unittest.TestCase):
 
-    def create_framework(self, *, model=None, tmpdir=None):
+    def create_framework(self,
+                         *,
+                         model: typing.Optional[ops.Model] = None,
+                         tmpdir: typing.Optional[pathlib.Path] = None):
         """Create a Framework object.
 
         By default operate in-memory; pass a temporary directory via the 'tmpdir'
@@ -122,8 +128,8 @@ def create_framework(self, *, model=None, tmpdir=None):
         framework = ops.Framework(
             SQLiteStorage(data_fpath),
             charm_dir,
-            meta=None,
-            model=model)
+            meta=model._cache._meta if model else ops.CharmMeta(),
+            model=model)  # type: ignore
         self.addCleanup(framework.close)
         return framework