Add GMTInvalidInput Error for Figure.coast

pygmt/base_plotting.py

@@ -9,6 +9,7 @@
 from pygmt.clib import Session
 from pygmt.exceptions import GMTError, GMTInvalidInput
 from pygmt.helpers import (
+    args_in_kwargs,
     build_arg_string,
     data_kind,
     dummy_context,
@@ -167,6 +168,11 @@ def coast(self, **kwargs):
 
         """
         kwargs = self._preprocess(**kwargs)
+        if not args_in_kwargs(args=["C", "G", "S", "I", "N", "Q", "W"], kwargs=kwargs):
+            raise GMTInvalidInput(
+                """At least one of the following arguments must be specified:
+                lakes, land, water, rivers, borders, Q, or shorelines"""
+            )
         with Session() as lib:
             lib.call_module("coast", build_arg_string(kwargs))
 

pygmt/tests/test_coast.py

@@ -3,6 +3,7 @@
 """
 import pytest
 from pygmt import Figure
+from pygmt.exceptions import GMTInvalidInput
 from pygmt.helpers.testing import check_figures_equal
 
 
@@ -97,6 +98,13 @@ def test_coast_world_mercator():
     return fig
 
 
+def test_coast_required_args():
+    "Test if fig.coast fails when not given required arguments"
+    fig = Figure()
+    with pytest.raises(GMTInvalidInput):
+        fig.coast(region="EG")
+
+
 @check_figures_equal()
 def test_coast_dcw_single():
     "Test passing a single country code to dcw"