new_contents: # -*- coding: utf-8 -*-
  
  
  import rasterio
  import pytest
  from math import pi
  
  from numpy import array
  from numpy.testing import assert_array_almost_equal
  
  from gdal2mbtiles.constants import EPSG_WEB_MERCATOR
  
  from gdal2mbtiles.gdal import SpatialReference
  
  
  # SEMI_MAJOR is a constant referring to the WGS84 Semi Major Axis.
  SEMI_MAJOR = 6378137.0
  
  # Note: web-Mercator = pseudo-Mercator = EPSG 3857
  # The extents of the web-Mercator are constants.
  # Since the projection is formed from a sphere the extents of the projection
  # form a square.
  # For the values of the extents refer to:
  # OpenLayer lib: http://docs.openlayers.org/library/spherical_mercator.html
  EPSG3857_EXTENT = pi * SEMI_MAJOR
  
  EPSG3857_EXTENTS = array([[-EPSG3857_EXTENT]*2, [EPSG3857_EXTENT]*2])
  
  epsg_3857_raster_path = 'tests/web_mercator_3857.tif'
  
  
  @pytest.fixture
  def epsg_3857_from_proj4():
      """
      Return a gdal spatial reference object with
      3857 crs using the ImportFromProj4 method.
      """
      ds_3857 = rasterio.open(epsg_3857_raster_path)
      spatial_ref = SpatialReference()
      spatial_ref.ImportFromProj4(ds_3857.crs.to_string())
      return spatial_ref
  
  
  @pytest.fixture
  def epsg_3857_from_epsg():
      """
      Return a gdal spatial reference object with
      3857 crs using the FromEPSG method.
      """
      spatial_ref = SpatialReference.FromEPSG(EPSG_WEB_MERCATOR)
      return spatial_ref
  
  
  def test_epsg_3857_proj4(epsg_3857_from_proj4):
      extents = epsg_3857_from_proj4.GetWorldExtents()
      extents = array(extents)
      assert_array_almost_equal(extents, EPSG3857_EXTENTS, decimal=3)
  
  
  def test_epsg_3857_from_epsg(epsg_3857_from_epsg):
      extents = epsg_3857_from_epsg.GetWorldExtents()
      extents = array(extents)
      assert_array_almost_equal(extents, EPSG3857_EXTENTS, decimal=3)
  
subject: Add test for the EPSG-3857 spatial reference.