Improve test coverage

nilmdb/server/nilmdb.py

@@ -111,9 +111,7 @@ class NilmDB(object):
         try:
             os.makedirs(self.basepath)
         except OSError as e:
-            if e.errno != errno.EEXIST: # pragma: no cover
-                # (no coverage, because it's hard to trigger this case
-                # if tests are run as root)
+            if e.errno != errno.EEXIST:
                 raise IOError("can't create tree " + self.basepath)
 
         # Our data goes inside it

tests/test_nilmdb.py

@@ -46,6 +46,10 @@ class Test00Nilmdb(object):  # named 00 so it runs first
         db.close()
         db.close()
 
+        with assert_raises(OSError) as e:
+            nilmdb.server.NilmDB("/dev/null/bogus")
+        in_("can't create tree", str(e.exception))
+
     def test_stream(self):
         db = nilmdb.server.NilmDB(testdb)
         eq_(db.stream_list(), [])