message: Add a test for polygons touching the tile border.
  The test demonstrates the issues that harp.gl has when
  stroking polygons with edges at the tile border.
diff: // tslint:disable:only-arrow-functions
  // Mocha discourages using arrow functions, see https://mochajs.org/#arrow-functions
  -import { GeoJson, Light, StyleSet, Theme } from "@here/harp-datasource-protocol";
  +import { FeatureCollection, GeoJson, Light, StyleSet, Theme } from "@here/harp-datasource-protocol";
  import { LookAtParams, MapView, MapViewEventNames } from "@here/harp-mapview";
  import { GeoJsonTiler } from "@here/harp-mapview-decoder/index-worker";
  import { GeoJsonDataProvider, OmvDataSource } from "@here/harp-omv-datasource";
  @@ -238,4 +238,53 @@ describe("MapView + OmvDataSource + GeoJsonDataProvider rendering test", functio
  }
  });
  });
  +
  + it("renders geometry touching the tile border", async function() {
  + this.timeout(5000);
  +
  + const geoJson: FeatureCollection = {
  + type: "FeatureCollection",
  + features: [
  + {
  + type: "Feature",
  + properties: {
  + "fill-color": "rgb(255,255,0)",
  + "stroke-color": "#000"
  + },
  + geometry: {
  + type: "Polygon",
  + coordinates: [
  + [
  + [0, 51.5],
  + [0.01, 51.5],
  + [0, 51.49],
  + [0, 51.5]
  + ]
  + ]
  + }
  + }
  + ]
  + };
  +
  + const ourStyle: StyleSet = [
  + {
  + when: ["==", ["geometry-type"], "Polygon"],
  + technique: "fill",
  + color: ["get", "fill-color"],
  + lineColor: ["get", "stroke-color"],
  + lineWidth: 1
  + }
  + ];
  +
  + await geoJsonTest({
  + mochaTest: this,
  + testImageName: "geojson-stroke-polygons-at-tile-border",
  + theme: { lights, styles: { geojson: ourStyle } },
  + geoJson,
  + lookAt: {
  + target: [0, 51.5],
  + zoomLevel: 13.4
  + }
  + });
  + });
  });
  