Throw an error if a MarkerClusterGroup is added to a map with no maxZoom. Fixes #189

spec/index.html

@@ -40,6 +40,7 @@
 	<script type="text/javascript" src="suites/CircleMarkerSupportSpec.js"></script>
 	<script type="text/javascript" src="suites/CircleSupportSpec.js"></script>
 
+	<script type="text/javascript" src="suites/onAddSpec.js"></script>
 	<script type="text/javascript" src="suites/clearLayersSpec.js"></script>
 	<script type="text/javascript" src="suites/eachLayerSpec.js"></script>
 	<script type="text/javascript" src="suites/eventsSpec.js"></script>

spec/suites/onAddSpec.js

@@ -0,0 +1,37 @@
+describe('onAdd', function () {
+	var map, div;
+	beforeEach(function () {
+		div = document.createElement('div');
+		div.style.width = '200px';
+		div.style.height = '200px';
+		document.body.appendChild(div);
+
+		map = L.map(div);
+
+		map.fitBounds(new L.LatLngBounds([
+			[1, 1],
+			[2, 2]
+		]));
+	});
+	afterEach(function () {
+		document.body.removeChild(div);
+	});
+
+
+	it('throws an error if maxZoom is not specified', function () {
+
+		var group = new L.MarkerClusterGroup();
+		var marker = new L.Marker([1.5, 1.5]);
+
+		group.addLayer(marker);
+
+		var ex = null;
+		try {
+			map.addLayer(group);
+		} catch (e) {
+			ex = e;
+		}
+
+		expect(ex).to.not.be(null);
+	});
+});

src/MarkerClusterGroup.js

@@ -370,6 +370,10 @@ L.MarkerClusterGroup = L.FeatureGroup.extend({
 		this._map = map;
 		var i, l, layer;
 
+		if (!isFinite(this._map.getMaxZoom())) {
+			throw "Map has no maxZoom specified";
+		}
+
 		this._featureGroup.onAdd(map);
 		this._nonPointGroup.onAdd(map);