added tests and small fixes for config

tests/test_config.py

@@ -0,0 +1,76 @@
+from os import environ
+import pytest
+from tempfile import NamedTemporaryFile
+
+from sanic import Sanic
+
+
+def test_load_from_object():
+    app = Sanic('test_load_from_object')
+    class Config:
+        not_for_config = 'should not be used'
+        CONFIG_VALUE = 'should be used'
+
+    app.config.from_object(Config)
+    assert 'CONFIG_VALUE' in app.config
+    assert app.config.CONFIG_VALUE == 'should be used'
+    assert 'not_for_config' not in app.config
+
+
+def test_load_from_file():
+    app = Sanic('test_load_from_file')
+    config = b"""
+VALUE = 'some value'
+condition = 1 == 1
+if condition:
+    CONDITIONAL = 'should be set'
+    """
+    with NamedTemporaryFile() as config_file:
+        config_file.write(config)
+        config_file.seek(0)
+        app.config.from_pyfile(config_file.name)
+        assert 'VALUE' in app.config
+        assert app.config.VALUE == 'some value'
+        assert 'CONDITIONAL' in app.config
+        assert app.config.CONDITIONAL == 'should be set'
+        assert 'condition' not in app.config
+
+
+def test_load_from_missing_file():
+    app = Sanic('test_load_from_missing_file')
+    with pytest.raises(IOError):
+        app.config.from_pyfile('non-existent file')
+
+
+def test_load_from_envvar():
+    app = Sanic('test_load_from_envvar')
+    config = b"VALUE = 'some value'"
+    with NamedTemporaryFile() as config_file:
+        config_file.write(config)
+        config_file.seek(0)
+        environ['APP_CONFIG'] = config_file.name
+        app.config.from_envvar('APP_CONFIG')
+        assert 'VALUE' in app.config
+        assert app.config.VALUE == 'some value'
+
+
+def test_load_from_missing_envvar():
+    app = Sanic('test_load_from_missing_envvar')
+    with pytest.raises(RuntimeError):
+        app.config.from_envvar('non-existent variable')
+
+
+def test_overwrite_exisiting_config():
+    app = Sanic('test_overwrite_exisiting_config')
+    app.config.DEFAULT = 1
+    class Config:
+        DEFAULT = 2
+
+    app.config.from_object(Config)
+    assert app.config.DEFAULT == 2
+
+
+def test_missing_config():
+    app = Sanic('test_missing_config')
+    with pytest.raises(AttributeError):
+        app.config.NON_EXISTENT