Set axis linecolor to black by default when converting from matplotlib figure

Author: robertoffmoura

plotly/matplotlylib/renderer.py

@@ -153,10 +153,10 @@ def open_axes(self, ax, props):
         self.axis_ct += 1
         # set defaults in axes
         xaxis = go.layout.XAxis(
-            anchor="y{0}".format(self.axis_ct), zeroline=False, ticks="inside"
+            anchor="y{0}".format(self.axis_ct), zeroline=False, ticks="inside", linecolor="black"
         )
         yaxis = go.layout.YAxis(
-            anchor="x{0}".format(self.axis_ct), zeroline=False, ticks="inside"
+            anchor="x{0}".format(self.axis_ct), zeroline=False, ticks="inside", linecolor="black"
         )
         # update defaults with things set in mpl
         mpl_xaxis, mpl_yaxis = mpltools.prep_xy_axis(

plotly/matplotlylib/tests/__init__.py

@@ -0,0 +1,4 @@
+import matplotlib
+
+matplotlib.use("Agg")
+import matplotlib.pyplot as plt

plotly/matplotlylib/tests/test_renderer.py

@@ -0,0 +1,12 @@
+import plotly.tools as tls
+
+from . import plt
+
+def test_axis_linecolor_defaults_to_black():
+    fig, ax = plt.subplots()
+    ax.plot([0, 1], [0, 1])
+
+    plotly_fig = tls.mpl_to_plotly(fig)
+
+    assert plotly_fig.layout.xaxis.linecolor == "black"
+    assert plotly_fig.layout.yaxis.linecolor == "black"