test error msg of _get_renderer (mpytools#207)

* test error msg of _get_renderer

* changelog

Author: mathause

CHANGELOG.md

@@ -22,7 +22,7 @@
 
 - Add python 3.13 to list of supported versions ([#158](https://github.com/mpytools/mplotutils/pull/158)).
 - Increased test coverage ([#180](https://github.com/mpytools/mplotutils/pull/180), [#181](https://github.com/mpytools/mplotutils/pull/181),
-  and [#182](https://github.com/mpytools/mplotutils/pull/182)).
+  [#182](https://github.com/mpytools/mplotutils/pull/182), and [#207](https://github.com/mpytools/mplotutils/pull/207)).
 
 ### Bug fixes
 

mplotutils/tests/test_get_renderer.py

@@ -13,3 +13,19 @@ def test_get_renderer(backend):
 
         with figure_context() as f:
             _get_renderer(f)
+
+
+def test_error_message_get_renderer():
+
+    # it's a fallback so should never be triggered - here I test the error message only
+
+    backend = matplotlib.get_backend()
+
+    class FakeFig:
+        def canvas(self): ...
+
+    with pytest.raises(
+        AttributeError,
+        match=f"Could not find a renderer for the '{backend}' backend. Please raise an issue",
+    ):
+        _get_renderer(FakeFig())