GeoStreamData

GeoStreamData is a library for generating geospatial data for property testing.

You can learn more about how to use StreamData and ExUnitPropertieshere.

Installation

def deps do
  [
    {:geo_stream_data, "~> 0.1.0"}
  ]
end

Usage

Most generally, there is a geometry() function that returns a stream of geometries of multiple types. LineStrings and Polygons that are generated are (mostly) guaranteed to be simple (having no non-consecutive line segments that intersect).

defmodule Envelope.PropertyTest do
  use ExUnit.Case
  use ExUnitProperties

  property "Two geometries are disjoint if their envelopes are disjoint" do
    check all geo1 <- GeoStreamData.geometry(),
              geo2 <- GeoStreamData.geometry(),
              env1 = Envelope.from_geo(geo1),
              env2 = Envelope.from_geo(geo2) do
      if !Envelope.intersects?(env1, env2) do
        assert Topo.disjoint?(geo1, geo2)
      end
    end
  end
end

There are also individual functions for generating streams of each type of geometry exclusively:

• point() - Geo.Point
• line_string() - Geo.LineString
• polygon() - Geo.Polygon
• multi_point() - Geo.MultiPoint
• multi_line_string() - Geo.MultiLineString
• multi_polygon() - Geo.MultiPolygon

property "A LineString contains a subset of its points" do
  check all line1 <- GeoStreamData.line_string(),
            a <- integer(0..(length(line1.coordinates) - 3)),
            b <- integer(2..(length(line1.coordinates) - a)) do
    line2 = %Geo.LineString{coordinates: Enum.slice(line1.coordinates, a..(a + b))}
    assert Topo.contains?(line1, line2)
  end
end