Fix .shared classing

Now that Graph#parentWays is cached, the specialized Graph#parentStructure
method is no longer necessary.

This commit also demonstrates that it's relatively easy to write specs for
rendering now!

test/index.html

@@ -139,6 +139,7 @@
     <script src="spec/renderer/hash.js"></script>
     <script src="spec/renderer/map.js"></script>
 
+    <script src="spec/svg/vertices.js"></script>
     <script src="spec/svg/tag_classes.js"></script>
 
     <script src="spec/ui/inspector.js"></script>

test/index_packaged.html

@@ -57,6 +57,7 @@
     <script src="spec/renderer/hash.js"></script>
     <script src="spec/renderer/map.js"></script>
 
+    <script src="spec/svg/vertices.js"></script>
     <script src="spec/svg/tag_classes.js"></script>
 
     <script src="spec/ui/inspector.js"></script>

test/spec/svg/vertices.js

@@ -0,0 +1,25 @@
+describe("iD.svg.Vertices", function () {
+    var surface,
+        projection = d3.geo.mercator(),
+        filter = d3.functor(true);
+
+    beforeEach(function () {
+        surface = d3.select(document.createElementNS('http://www.w3.org/2000/svg', 'svg'));
+
+        surface.append('g')
+            .attr('class', 'layer-hit');
+    });
+
+    // TODO: fill out
+
+    it("adds the .shared class to vertices that are members of two or more ways", function () {
+        var node = iD.Node({loc: [0, 0]}),
+            way1 = iD.Way({nodes: [node.id]}),
+            way2 = iD.Way({nodes: [node.id]}),
+            graph = iD.Graph([node, way1, way2]);
+
+        surface.call(iD.svg.Vertices(), graph, [node], filter, projection);
+
+        expect(surface.select('.vertex').classed('shared')).to.equal(true);
+    });
+});