Improves test coverage

* Refactors tests
* Adds more tests

Author: palnabarun

mplaltair/tests/test_convert.py

@@ -5,7 +5,22 @@
 
 from mplaltair import convert
 
-df = pd.DataFrame({'quant': [1, 1.5, 2], 'ord': [0, 1, 2], 'nom': ['A', 'B', 'C']})
+df = pd.DataFrame({
+    'quant': [1, 1.5, 2],
+    'ord': [0, 1, 2],
+    'nom': ['A', 'B', 'C'],
+    'temp': [10, 20, 30]
+})
+
+def test_encoding_not_provided():
+    chart_spec = alt.Chart(df).mark_point().to_dict()
+    with pytest.raises(ValueError):
+        convert(chart_spec)
+
+def test_invalid_encodings():
+    chart_spec = alt.Chart(df).encode(x2='quant').mark_point().to_dict()
+    with pytest.raises(ValueError):
+        convert(chart_spec)
 
 @pytest.mark.parametrize('channel', ['quant', 'ord', 'nom'])
 def test_convert_x_success(channel):
@@ -45,9 +60,9 @@ def test_convert_color_fail():
     with pytest.raises(KeyError):
         convert(chart_spec)
 
-@pytest.mark.parametrize('channel', ['quant', 'ord'])
-def test_convert_fill(channel):
-    chart_spec = alt.Chart(df).encode(fill=channel).mark_point().to_dict()
+@pytest.mark.parametrize('channel,type', [('quant', 'Q'), ('ord', 'O')])
+def test_convert_fill(channel, type):
+    chart_spec = alt.Chart(df).encode(fill='{}:{}'.format(channel, type)).mark_point().to_dict()
     mapping = convert(chart_spec)
     assert list(mapping['c']) == list(df[channel].values)
 
@@ -56,14 +71,19 @@ def test_convert_fill_success_nominal():
     with pytest.raises(NotImplementedError):
         convert(chart_spec)
 
+def test_convert_fill_success_temporal():
+    chart_spec = alt.Chart(df).encode(fill='temp:T').mark_point().to_dict()
+    with pytest.raises(NotImplementedError):
+        convert(chart_spec)
+
 def test_convert_fill_fail():
     chart_spec = alt.Chart(df).encode(fill='b:N').mark_point().to_dict()
     with pytest.raises(KeyError):
         convert(chart_spec)
 
-@pytest.mark.parametrize('channel', ['quant', 'ord'])
-def test_convert_size_success(channel):
-    chart_spec = alt.Chart(df).encode(size=channel).mark_point().to_dict()
+@pytest.mark.parametrize('channel,type', [('quant', 'Q'), ('ord', 'O')])
+def test_convert_size_success(channel, type):
+    chart_spec = alt.Chart(df).encode(size='{}:{}'.format(channel, type)).mark_point().to_dict()
     mapping = convert(chart_spec)
     assert list(mapping['s']) == list(df[channel].values)
 
@@ -72,6 +92,11 @@ def test_convert_size_success_nominal():
     with pytest.raises(NotImplementedError):
         convert(chart_spec)
 
+def test_convert_size_success_temporal():
+    chart_spec = alt.Chart(df).encode(size='temp:T').mark_point().to_dict()
+    with pytest.raises(NotImplementedError):
+        convert(chart_spec)
+
 def test_convert_size_fail():
     chart_spec = alt.Chart(df).encode(size='b:N').mark_point().to_dict()
     with pytest.raises(KeyError):