adding coverage for exceptions

NOTES.md

@@ -11,3 +11,7 @@
 1.  wait for Travis to show passing
 1.  build the packages: `python setup.py sdist bdist_wheel`
 1.  upload to pypi: `twine upload dist/*`
+
+## Coverage testing
+
+    coverage run --source=yamicache -p -m py.test && coverage combine && coverage report -m

tests/test_exceptions.py

@@ -0,0 +1,17 @@
+import pytest
+from yamicache.yamicache import Cache
+
+
+def test_object_creation():
+    with pytest.raises(ValueError):
+        Cache(default_timeout=0.5)
+
+
+def test_function():
+    c = Cache()
+
+    with pytest.raises(ValueError):
+
+        @c.cached(timeout=0.5)
+        def t1():
+            pass