Add testing for read_postgis function

It also installs postgis and creates a simple database filled with the borough
data. A new requirements.test.txt file is created so that not everybody
installing geopandas is required to install the packages for testing, psycopg2
in this case.

.travis.yml

@@ -10,10 +10,20 @@ env:
 before_install:
   - sudo add-apt-repository -y ppa:ubuntugis/ubuntugis-unstable
   - sudo apt-get update
-  - sudo apt-get install gdal-bin libgdal-dev
+  - sudo apt-get install gdal-bin libgdal-dev postgresql-9.1-postgis-2.0
+  - sudo -u postgres psql -c "drop database if exists test_geopandas"
+  - sudo -u postgres psql -c "create database test_geopandas"
+  - sudo -u postgres psql -c "create extension postgis" -d test_geopandas
+  - ogrinfo --version
+  - ogrinfo --formats
+  - wget http://www.nyc.gov/html/dcp/download/bytes/nybb_13a.zip
+  - unzip nybb_13a.zip
+  - sudo -u postgres ogr2ogr -nlt MULTIPOLYGON -f "PostgreSQL" PG:"user=postgres dbname=test_geopandas" -lco PRECISION=NO -lco GEOMETRY_NAME="geom" nybb_13a/nybb.shp
+
 
 install:
   - pip install -r requirements.txt --use-mirrors
+  - pip install -r requirements.test.txt --use-mirrors
   - git clone git://github.com/pydata/pandas.git
   - cd pandas
   - git checkout $PANDAS_VERSION

requirements.test.txt

@@ -0,0 +1 @@
+psycopg2>=2.5.1

tests/test_geodataframe.py

@@ -7,6 +7,7 @@ import urllib2
 
 import numpy as np
 from shapely.geometry import Point, Polygon
+import psycopg2
 
 from geopandas import GeoDataFrame
 
@@ -82,3 +83,26 @@ class TestDataFrame(unittest.TestCase):
         lonlat = df2.to_crs(epsg=4326)
         utm = lonlat.to_crs(epsg=26918)
         self.assertTrue(all(df2['geometry'].almost_equals(utm['geometry'], decimal=2)))
+
+    def _validate_sql(self, df):
+        # Make sure all the columns are there and the geometries
+        # were properly loaded as MultiPolygons
+        columns = ('borocode', 'boroname', 'shape_leng', 'shape_area')
+        for col in columns:
+            self.assertTrue(col in df.columns, 'Column {} missing'.format(col))
+        self.assertTrue(all(df['geometry'].type == 'MultiPolygon'))
+
+    def test_read_postgis_default(self):
+        con = psycopg2.connect(dbname='test_geopandas')
+        sql = "SELECT * FROM nybb;"
+        df = GeoDataFrame.read_postgis(sql, con)
+        self._validate_sql(df)
+
+    def test_read_postgis_custom_geom_col(self):
+        con = psycopg2.connect(dbname='test_geopandas')
+        sql = """SELECT
+                  borocode, boroname, shape_leng, shape_area,
+                  geom AS __geometry__
+                  FROM nybb;"""
+        df = GeoDataFrame.read_postgis(sql, con, geom_col='__geometry__')
+        self._validate_sql(df)