Adding tests for tile providers

Author: darribas

tests/test_providers.py

@@ -0,0 +1,11 @@
+import contextily as ctx
+import contextily.tile_providers as tilers
+
+def test_sources():
+    # NOTE: only tests they download, does not check pixel values
+    w, s, e, n = (-106.6495132446289, 25.845197677612305, 
+            -93.50721740722656, 36.49387741088867)
+    sources = [i for i in dir(tilers) if i[0] != '_']
+    for src in sources:
+        img, ext = ctx.bounds2img(w, s, e, n, 4, ll=True)
+