add download tests for Caltech(101|256) (pytorch#2731)

* add download tests for Caltech(101|256)

* lint

test/test_datasets_download.py

@@ -45,13 +45,23 @@ def inner_wrapper(request, *args, **kwargs):
 
 
 @contextlib.contextmanager
-def log_download_attempts(patch=True):
-    urls_and_md5s = set()
-    with unittest.mock.patch("torchvision.datasets.utils.download_url", wraps=None if patch else download_url) as mock:
+def log_download_attempts(urls_and_md5s=None, patch=True, patch_auxiliaries=None):
+    if urls_and_md5s is None:
+        urls_and_md5s = set()
+    if patch_auxiliaries is None:
+        patch_auxiliaries = patch
+
+    with contextlib.ExitStack() as stack:
+        download_url_mock = stack.enter_context(
+            unittest.mock.patch("torchvision.datasets.utils.download_url", wraps=None if patch else download_url)
+        )
+        if patch_auxiliaries:
+            # download_and_extract_archive
+            stack.enter_context(unittest.mock.patch("torchvision.datasets.utils.extract_archive"))
         try:
             yield urls_and_md5s
         finally:
-            for args, kwargs in mock.call_args_list:
+            for args, kwargs in download_url_mock.call_args_list:
                 url = args[0]
                 md5 = args[-1] if len(args) == 4 else kwargs.get("md5")
                 urls_and_md5s.add((url, md5))
@@ -105,15 +115,14 @@ def __init__(self, url, md5=None, id=None):
         self.md5 = md5
         self.id = id or url
 
+    def __repr__(self):
+        return self.id
 
-def make_parametrize_kwargs(download_configs):
-    argvalues = []
-    ids = []
-    for config in download_configs:
-        argvalues.append((config.url, config.md5))
-        ids.append(config.id)
 
-    return dict(argnames="url, md5", argvalues=argvalues, ids=ids)
+def make_download_configs(urls_and_md5s, name=None):
+    return [
+        DownloadConfig(url, md5=md5, id=f"{name}, {url}" if name is not None else None) for url, md5 in urls_and_md5s
+    ]
 
 
 def places365():
@@ -124,10 +133,40 @@ def places365():
 
                 datasets.Places365(root, split=split, small=small, download=True)
 
-    return [DownloadConfig(url, md5=md5, id=f"Places365, {url}") for url, md5 in urls_and_md5s]
+    return make_download_configs(urls_and_md5s, "Places365")
+
+
+def caltech101():
+    try:
+        with log_download_attempts() as urls_and_md5s:
+            datasets.Caltech101(".", download=True)
+    except Exception:
+        pass
+
+    return make_download_configs(urls_and_md5s, "Caltech101")
+
+
+def caltech256():
+    try:
+        with log_download_attempts() as urls_and_md5s:
+            datasets.Caltech256(".", download=True)
+    except Exception:
+        pass
+
+    return make_download_configs(urls_and_md5s, "Caltech256")
+
+
+def make_parametrize_kwargs(download_configs):
+    argvalues = []
+    ids = []
+    for config in download_configs:
+        argvalues.append((config.url, config.md5))
+        ids.append(config.id)
+
+    return dict(argnames=("url", "md5"), argvalues=argvalues, ids=ids)
 
 
-@pytest.mark.parametrize(**make_parametrize_kwargs(itertools.chain(places365(),)))
+@pytest.mark.parametrize(**make_parametrize_kwargs(itertools.chain(places365(), caltech101(), caltech256())))
 def test_url_is_accessible(url, md5):
     retry(lambda: assert_url_is_accessible(url))