Add test for font selection by texmanager.

Author: anntzer

lib/matplotlib/tests/test_texmanager.py

@@ -1,11 +1,13 @@
+from pathlib import Path
+import re
+
 import matplotlib.pyplot as plt
 from matplotlib.texmanager import TexManager
+import pytest
 
 
 def test_fontconfig_preamble():
-    """
-    Test that the preamble is included in _fontconfig
-    """
+    """Test that the preamble is included in _fontconfig."""
     plt.rcParams['text.usetex'] = True
 
     tm1 = TexManager()
@@ -16,3 +18,22 @@ def test_fontconfig_preamble():
     font_config2 = tm2.get_font_config()
 
     assert font_config1 != font_config2
+
+
+@pytest.mark.parametrize(
+    "rc, preamble, family", [
+        ({"font.family": "sans-serif", "font.sans-serif": "helvetica"},
+         r"\usepackage{helvet}", r"\sffamily"),
+        ({"font.family": "serif", "font.serif": "palatino"},
+         r"\usepackage{mathpazo}", r"\rmfamily"),
+        ({"font.family": "cursive", "font.cursive": "zapf chancery"},
+         r"\usepackage{chancery}", r"\rmfamily"),
+        ({"font.family": "monospace", "font.monospace": "courier"},
+         r"\usepackage{courier}", r"\ttfamily"),
+    ])
+def test_font_selection(rc, preamble, family):
+    plt.rcParams.update(rc)
+    tm = TexManager()
+    src = Path(tm.make_tex("hello, world", fontsize=12)).read_text()
+    assert preamble in src
+    assert [*re.findall(r"\\\w+family", src)] == [family]