8th day of python challenges 111-117

venv/lib/python3.6/site-packages/pandas/tests/plotting/test_backend.py

@@ -0,0 +1,38 @@
+import pytest
+
+import pandas
+
+
+def test_matplotlib_backend_error():
+    msg = (
+        "matplotlib is required for plotting when the default backend "
+        '"matplotlib" is selected.'
+    )
+    try:
+        import matplotlib  # noqa
+    except ImportError:
+        with pytest.raises(ImportError, match=msg):
+            pandas.set_option("plotting.backend", "matplotlib")
+
+
+def test_backend_is_not_module():
+    msg = (
+        '"not_an_existing_module" does not seem to be an installed module. '
+        "A pandas plotting backend must be a module that can be imported"
+    )
+    with pytest.raises(ValueError, match=msg):
+        pandas.set_option("plotting.backend", "not_an_existing_module")
+
+
+def test_backend_is_correct(monkeypatch):
+    monkeypatch.setattr(
+        "pandas.core.config_init.importlib.import_module", lambda name: None
+    )
+    pandas.set_option("plotting.backend", "correct_backend")
+    assert pandas.get_option("plotting.backend") == "correct_backend"
+
+    # Restore backend for other tests (matplotlib can be not installed)
+    try:
+        pandas.set_option("plotting.backend", "matplotlib")
+    except ImportError:
+        pass