[REF] refactor test surface plotting (nilearn#4966)

nilearn/plotting/tests/conftest.py

@@ -0,0 +1,35 @@
+import pytest
+
+
+@pytest.fixture(scope="function")
+def pyplot():
+    """Set up and teardown fixture for matplotlib.
+
+    This fixture checks if we can import matplotlib. If not, the tests will be
+    skipped. Otherwise, we close the figures before and after running the
+    functions.
+
+    Returns
+    -------
+    pyplot : module
+        The ``matplotlib.pyplot`` module.
+    """
+    pyplot = pytest.importorskip("matplotlib.pyplot")
+    pyplot.close("all")
+    yield pyplot
+    pyplot.close("all")
+
+
+@pytest.fixture(scope="function")
+def plotly():
+    """Check if we can import plotly.
+
+    If not, the tests will be skipped.
+
+    Returns
+    -------
+    plotly : module
+        The ``plotly`` module.
+    """
+    plotly = pytest.importorskip("plotly")
+    yield plotly