Add travis config to test on sqlite, postgres, mysql

.travis.yml

@@ -4,8 +4,16 @@ python:
 - '3.3'
 - '2.7'
 - '2.6'
+env:
+- DATABASE_URL=sqlite:///:memory:
+- DATABASE_URL=postgresql+psycopg2://postgres@127.0.0.1/dataset
+- DATABASE_URL=mysql+pymysql://travis@127.0.0.1/dataset?charset=utf8
 install:
-- pip install flake8
+- pip install flake8 psycopg2 pymysql
+before_script:
+- sh -c "if [ '$DATABASE_URL' = 'postgresql+psycopg2://postgres@127.0.0.1/dataset' ]; then psql -c 'DROP DATABASE IF EXISTS dataset;' -U postgres; fi"
+- sh -c "if [ '$DATABASE_URL' = 'postgresql+psycopg2://postgres@127.0.0.1/dataset' ]; then psql -c 'create database dataset;' -U postgres; fi"
+- sh -c "if [ '$DATABASE_URL' = 'mysql+pymysql://travis@127.0.0.1/dataset?charset=utf8' ]; then mysql -e 'create database IF NOT EXISTS dataset DEFAULT CHARACTER SET utf8 DEFAULT COLLATE utf8_general_ci;'; fi"
 script:
 - flake8 --ignore=E501,E123,E124,E126,E127,E128 dataset test
 - python setup.py test

test/test_persistence.py

@@ -13,20 +13,12 @@ from .sample_data import TEST_DATA, TEST_CITY_1
 class DatabaseTestCase(unittest.TestCase):
 
     def setUp(self):
-        self.old_db_url = os.environ.get('DATABASE_URL')
-        os.environ['DATABASE_URL'] = 'sqlite:///:memory:'
-        self.db = connect('sqlite:///:memory:')
+        os.environ.setdefault('DATABASE_URL', 'sqlite:///:memory:')
+        self.db = connect(os.environ['DATABASE_URL'])
         self.tbl = self.db['weather']
         for row in TEST_DATA:
             self.tbl.insert(row)
 
-    def tearDown(self):
-        # ensure env variable was unset
-        if self.old_db_url is None:
-            del os.environ['DATABASE_URL']
-        else:
-            os.environ['DATABASE_URL'] = self.old_db_url
-
     def test_valid_database_url(self):
         assert self.db.url, os.environ['DATABASE_URL']