From d2824ca074478ea7c66f618b4bd13a58b081649a Mon Sep 17 00:00:00 2001
From: chrishavlin <chris.havlin@gmail.com>
Date: Mon, 9 Oct 2023 11:58:16 -0500
Subject: [PATCH 1/3] mv fn none check to main function, add test

---
 yt/loaders.py                | 17 +++++++++--------
 yt/tests/test_load_sample.py |  4 ++++
 2 files changed, 13 insertions(+), 8 deletions(-)

diff --git a/yt/loaders.py b/yt/loaders.py
index 0e9ff8f2c73..2876db51113 100644
--- a/yt/loaders.py
+++ b/yt/loaders.py
@@ -1487,14 +1487,6 @@ def _get_sample_data(
     # broadcast to other processes during parallel execution).
     import tarfile
 
-    if fn is None:
-        print(
-            "One can see which sample datasets are available at: https://yt-project.org/data\n"
-            "or alternatively by running: yt.sample_data.api.get_data_registry_table()",
-            file=sys.stderr,
-        )
-        return None
-
     from yt.sample_data.api import (
         _download_sample_data_file,
         _get_test_data_dir_path,
@@ -1663,6 +1655,15 @@ def load_sample(
     - Corresponding sample data live at https://yt-project.org/data
 
     """
+
+    if fn is None:
+        print(
+            "One can see which sample datasets are available at: https://yt-project.org/data\n"
+            "or alternatively by running: yt.sample_data.api.get_data_registry_table()",
+            file=sys.stderr,
+        )
+        return None
+
     loadable_path, load_kwargs = _get_sample_data(
         fn, progressbar=progressbar, timeout=timeout, **kwargs
     )
diff --git a/yt/tests/test_load_sample.py b/yt/tests/test_load_sample.py
index 18f6b743732..9d4880caa59 100644
--- a/yt/tests/test_load_sample.py
+++ b/yt/tests/test_load_sample.py
@@ -196,3 +196,7 @@ def test_data_dir_broken():
     )
     with pytest.warns(UserWarning, match=msg):
         load_sample("ToroShockTube")
+
+
+def test_filename_none():
+    assert load_sample(None) is None

From b018e64e2e980f33854cca663691d0ed87380f13 Mon Sep 17 00:00:00 2001
From: chrishavlin <chris.havlin@gmail.com>
Date: Mon, 9 Oct 2023 11:59:30 -0500
Subject: [PATCH 2/3] adjust test

---
 yt/tests/test_load_sample.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/yt/tests/test_load_sample.py b/yt/tests/test_load_sample.py
index 9d4880caa59..31d7d1a511e 100644
--- a/yt/tests/test_load_sample.py
+++ b/yt/tests/test_load_sample.py
@@ -199,4 +199,4 @@ def test_data_dir_broken():
 
 
 def test_filename_none():
-    assert load_sample(None) is None
+    assert load_sample() is None

From 7fe4c2da9e63c2c0d67d8de795c15b7e7c200488 Mon Sep 17 00:00:00 2001
From: chrishavlin <chris.havlin@gmail.com>
Date: Mon, 9 Oct 2023 12:05:29 -0500
Subject: [PATCH 3/3] check sys.stderr in new test

---
 yt/tests/test_load_sample.py | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/yt/tests/test_load_sample.py b/yt/tests/test_load_sample.py
index 31d7d1a511e..c5b5189bc46 100644
--- a/yt/tests/test_load_sample.py
+++ b/yt/tests/test_load_sample.py
@@ -198,5 +198,7 @@ def test_data_dir_broken():
         load_sample("ToroShockTube")
 
 
-def test_filename_none():
+def test_filename_none(capsys):
     assert load_sample() is None
+    captured = capsys.readouterr()
+    assert "yt.sample_data.api.get_data_registry_table" in captured.err