TST: Avoid using os.devnull for path tests

On wasm, this file doesn't support seeking, which is sometimes necessary
depending on file type.

Author: QuLogic

lib/matplotlib/tests/test_backend_pdf.py

@@ -1,7 +1,6 @@
 import datetime
 import decimal
 import io
-import os
 from pathlib import Path
 
 import numpy as np
@@ -291,8 +290,8 @@ def test_text_urls_tex():
             assert annot.Rect[1] == decimal.Decimal('0.7') * 72
 
 
-def test_pdfpages_fspath():
-    with PdfPages(Path(os.devnull)) as pdf:
+def test_pdfpages_fspath(tmp_path):
+    with PdfPages(tmp_path / 'unused.pdf') as pdf:
         pdf.savefig(plt.figure())
 
 

lib/matplotlib/tests/test_image.py

@@ -214,8 +214,8 @@ def test_imsave_rgba_origin(origin):
 
 
 @pytest.mark.parametrize("fmt", ["png", "pdf", "ps", "eps", "svg"])
-def test_imsave_fspath(fmt):
-    plt.imsave(Path(os.devnull), np.array([[0, 1]]), format=fmt)
+def test_imsave_fspath(fmt, tmp_path):
+    plt.imsave(tmp_path / f'unused.{fmt}', np.array([[0, 1]]), format=fmt)
 
 
 def test_imsave_color_alpha():