Add two unit tests for join method

tests/test_maps.py

@@ -44,6 +44,7 @@ def test_setup_map():
         'width': 960,
         'height': 500,
         'features': [],
+        'attr':'Map tiles by Stamen Design, CC BY 3.0 - Map data © OpenStreetMap'
     }
     """ Tests features as NumPy array. """
     kwargs2 = {
@@ -56,6 +57,7 @@ def test_setup_map():
             ds.Marker(51.514, -0.139), 
             ds.Marker(51.519, -0.132)
         ]),
+        'attr':'Map tiles by Stamen Design, CC BY 3.0 - Map data © OpenStreetMap'
     }
     ds.Map(**kwargs1).show()
     ds.Map(**kwargs2).show()

tests/test_tables.py

@@ -103,6 +103,11 @@ def scrabble_table2():
         'pointsplus1', [2, 3, 3, 11],
         ])
 
+@pytest.fixture(scope='function')
+def empty_table():
+    """Setup empty table"""
+    return Table().with_columns("A",[])
+
 
 def assert_equal(string1, string2):
     string1, string2 = str(string1), str(string2)
@@ -1660,6 +1665,21 @@ def test_join_without_other_label(table, table2):
     2      | c      | 3     | two
     """)
 
+def test_join_with_empty_table(table, empty_table):
+    result = empty_table._join('points', table)
+    assert result is None
+
+    result = table._join('points', empty_table)
+    assert result is None
+
+def test_join_without_other_label(table, table2):
+    result = table._join('points', table2)
+    assert result is not None
+
+
+
+
+
 
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