Start adding tests

modules/actions/flip.js

@@ -5,8 +5,9 @@ Only operates on "area" ways
 
 export function actionFlip(wayId, isVertical, projection) {
 
-    return function (graph) {
+    return function (graph) {        
         const targetWay = graph.entity(wayId);
+
         // If the way is not an area, we will not process it
         if (!targetWay.isArea()) {
             // return input graph without changes

test/spec/actions/flip.js

@@ -0,0 +1,34 @@
+describe('iD.actionFlip', function() {
+    var projection = d3.geoMercator();
+
+     it('flips horizontally - does not change graph length', function () {
+        var graph = iD.Graph([
+                iD.Node({id: 'a', loc: [0, 0]}),
+                iD.Node({id: 'b', loc: [2, 0]}),
+                iD.Node({id: 'c', loc: [2, 2]}),
+                iD.Node({id: 'd', loc: [0, 2]}),
+                iD.Way({id: '-', nodes: ['a', 'b', 'c', 'd', 'a'], tags: { area: 'yes'}})
+            ]);
+
+        graph = iD.actionFlip('-', false, projection)(graph);
+
+        expect(graph.entity('-').nodes).to.have.length(5);
+     });
+
+     it('flips horizontally - alters x value', function () {
+        var graph = iD.Graph([
+                iD.Node({id: 'a', loc: [0, 0]}),
+                iD.Node({id: 'b', loc: [2, 0]}),
+                iD.Node({id: 'c', loc: [2, 2]}),
+                iD.Node({id: 'd', loc: [0, 2]}),
+                                iD.Way({id: '-', nodes: ['a', 'b', 'c', 'd', 'a'], tags: { area: 'yes'}})
+            ]);
+        graph = iD.actionFlip('-', false, projection)(graph);
+
+         expect(graph.entity('a').loc[0]).to.equal(2); // A should be 2,0 now
+         expect(graph.entity('b').loc[0]).to.equal(0); // B should be 0,0 now
+         expect(graph.entity('c').loc[0]).to.equal(0); // C should be 0,2 now
+         expect(graph.entity('d').loc[0]).to.equal(2); // D should be 2,0 now
+    });
+
+});