--- /dev/null
+require 'test_helper'
+
+class ShortLinkTest < ActiveSupport::TestCase
+ ##
+ # tests that encoding and decoding are working to within
+ # the acceptable quantisation range.
+ def test_encode_decode
+ cases = Array.new
+ 1000.times do
+ cases << [ 180.0 * rand - 90.0, 360.0 * rand - 180.0, (18 * rand).to_i ]
+ end
+
+ cases.each do |lat, lon, zoom|
+ lon2, lat2, zoom2 = ShortLink.decode(ShortLink.encode(lon, lat, zoom))
+ # zooms should be identical
+ assert_equal zoom, zoom2, "Decoding a encoded short link gives different zoom for (#{lat}, #{lon}, #{zoom})."
+ # but the location has a quantisation error introduced at roughly
+ # one pixel (i.e: zoom + 8). the sqrt(5) is because each position
+ # has an extra bit of accuracy in the lat coordinate, due to the
+ # smaller range.
+ distance = Math.sqrt((lat - lat2) ** 2 + (lon - lon2) ** 2)
+ max_distance = 360.0 / (1 << (zoom + 8)) * 0.5 * Math.sqrt(5)
+ assert max_distance > distance, "Maximum expected error exceeded: #{max_distance} <= #{distance} for (#{lat}, #{lon}, #{zoom})."
+ end
+ end
+
+ ##
+ # test that links are backwards-compatible, so any old links with
+ # the deprecated @ characters in them still work properly.
+ def test_deprecated_at_sign
+ cases = [["~v2juONc--", "@v2juONc--"],
+ ["as3I3GpG~-", "as3I3GpG@-"],
+ ["D~hV--", "D@hV--"],
+ ["CO0O~m8--", "CO0O@m8--"]]
+
+ cases.each do |new_code, old_code|
+ assert_equal ShortLink.decode(old_code), ShortLink.decode(new_code),
+ "old (#{old_code}) and new (#{new_code}) should decode to the same location."
+ end
+ end
+end