Add tests

tests/test_data_versus_default.py

+"""
+The difference between data and default is that default will update the
+defaults and persist between multiple load operations whereas data will
+only set the immediate values and not persist over multiple loads.
+"""
+import scriptconfig as scfg
+import pytest
+
+
+def generate_dataconfig_instance_variants():
+    # In its simplest incarnation, the config class specifies default values.
+    # For each configuration parameter.
+    class ExampleConfig1(scfg.DataConfig):
+        num = 1
+        mode = 'bar'
+        ignore = ['baz', 'biz']
+
+    # Test with data configs
+    config = ExampleConfig1()
+    yield config, 'dataconfig'
+
+    class ExampleConfig2(scfg.Config):
+        __default__ = dict(
+            num=1,
+            mode='bar',
+            ignore=['baz', 'biz'],
+        )
+    # Test with original configs
+    config = ExampleConfig2()
+    yield config, 'orig-dunder-default'
+
+    class ExampleConfig3(scfg.Config):
+        default = dict(
+            num=1,
+            mode='bar',
+            ignore=['baz', 'biz'],
+        )
+    config = ExampleConfig3()
+    yield config, 'orig-default'
+
+
+@pytest.mark.parametrize('config, test_name', generate_dataconfig_instance_variants())
+def test_data_vs_default(config, test_name):
+    assert config['num'] == 1
+
+    # Using load(data=kwargs) unions kwargs with the existing defaults
+    # but does not change the defaults
+    kwargs = {'num': 2}
+    config = config.load(data=kwargs)
+    assert config['num'] == 2
+    assert config['mode'] == 'bar'
+
+    # Calling load again will reset any unspecified params to the defaults
+    kwargs = {'mode': 'foo'}
+    config = config.load(data=kwargs)
+    assert config['num'] == 1
+    assert config['mode'] == 'foo'
+
+    # Using load(default=kwargs) changes the defaults and then does the same
+    # process.
+    kwargs = {'num': 2}
+    config = config.load(default=kwargs)
+    assert config['num'] == 2
+    assert config['mode'] == 'bar'
+
+    # Calling again will show the defaults are changed
+    kwargs = {'mode': 'foo'}
+    config = config.load(default=kwargs)
+    assert config['num'] == 2
+    assert config['mode'] == 'foo'
+
+    config = config.load()
+    assert config['num'] == 2
+    assert config['mode'] == 'foo'
+
+    # Test that cmdline will overload a default
+    config = config.load(cmdline='--num=3', default={'num': 4})
+    assert config['num'] == 3
+    # But the new default should persist
+    config = config.load()
+    assert config['num'] == 4
+
+    # Test that data will overload a default
+    config = config.load(data=dict(num=10), default={'num': 5})
+    assert config['num'] == 10
+    # But the new default should persist
+    config = config.load()
+    assert config['num'] == 5