Add test setup to make Leaflet think JSDOM supports SVG

Author: mikeu

jest.config.js

@@ -5,6 +5,9 @@ module.exports = {
   coverageDirectory: 'coverage',
   restoreMocks: true,
   moduleFileExtensions: ['js', 'jsx', 'json', 'vue'],
+  setupFiles: [
+    '<rootDir>/tests/setup.js'
+  ],
   transform: {
     '^.+\\.vue$': 'vue-jest',
     '.+\\.(css|styl|less|sass|scss|svg|png|jpg|ttf|woff|woff2)$':

tests/setup.js

@@ -0,0 +1,13 @@
+// Perform any pre-test setup required.
+
+// Trick Leaflet into thinking that JSDOM has SVG support.
+// See: https://stackoverflow.com/a/54384719/607408
+const createElementNSOrig = global.document.createElementNS;
+global.document.createElementNS = function (uri, name) {
+  const element = createElementNSOrig.apply(this, arguments);
+  if (uri === 'http://www.w3.org/2000/svg' && name === 'svg') {
+    element.createSVGRect = function () {};
+  }
+
+  return element;
+};