Add test and fix some corner cases.

src/components/MapProperty.coffee

@@ -41,7 +41,7 @@ class MapProperty extends noflo.Component
     mapData: (data) ->
         newData = {}
         for property, value of data
-            if @map[property]
+            if property of @map
                 property = @map[property]
 
             for expression, replacement of @regexps
@@ -51,7 +51,13 @@ class MapProperty extends noflo.Component
 
                 property = property.replace regexp, replacement
 
-            newData[property] = value
+            if property of newData
+                if Array.isArray newData[property]
+                    newData[property].push value
+                else
+                    newData[property] = [newData[property], value]
+            else
+                newData[property] = value
         @outPorts.out.send newData
 
 exports.getComponent = -> new MapProperty

test/MapProperty.coffee

@@ -0,0 +1,105 @@
+mapper = require "../src/components/MapProperty"
+socket = require "../src/lib/InternalSocket"
+
+setupComponent = ->
+    c = mapper.getComponent()
+    ins = socket.createSocket()
+    map = socket.createSocket()
+    out = socket.createSocket()
+    c.inPorts.in.attach ins
+    c.inPorts.map.attach map
+    c.outPorts.out.attach out
+    return [c, ins, map, out]
+
+o = { a:1, b:2, c:3 }
+
+exports["test no map"] = (test) ->
+    [c, ins, map, out] = setupComponent()
+    output = []
+    out.on "data", (data) ->
+        output.push data
+    out.once "disconnect", ->
+        test.same output, [{ a:1, b:2, c:3 }]
+        test.done()
+    ins.send o
+    ins.disconnect()
+
+exports["test map to letter key"] = (test) ->
+    [c, ins, map, out] = setupComponent()
+    output = []
+    out.on "data", (data) ->
+        output.push data
+    out.once "disconnect", ->
+        test.same output, [{ d:1, b:2, c:3 }]
+        test.done()
+    map.send {a:"d"}
+    map.disconnect
+    ins.send o
+    ins.disconnect()
+
+exports["test map to colliding key"] = (test) ->
+    [c, ins, map, out] = setupComponent()
+    output = []
+    out.on "data", (data) ->
+        output.push data
+    out.once "disconnect", ->
+        test.same output, [{ b:[1,2], c:3 }]
+        test.done()
+    map.send {a:"b"}
+    map.disconnect
+    ins.send o
+    ins.disconnect()
+
+exports["test map to 0 key"] = (test) ->
+    [c, ins, map, out] = setupComponent()
+    output = []
+    out.on "data", (data) ->
+        output.push data
+    out.once "disconnect", ->
+        test.same output, [{ 0:1, b:2, c:3 }]
+        test.done()
+    map.send {a:0}
+    map.disconnect
+    ins.send o
+    ins.disconnect()
+
+exports["test map to null key"] = (test) ->
+    [c, ins, map, out] = setupComponent()
+    output = []
+    out.on "data", (data) ->
+        output.push data
+    out.once "disconnect", ->
+        test.same output, [{ null:1, b:2, c:3 }]
+        test.done()
+    map.send {a:null}
+    map.disconnect
+    ins.send o
+    ins.disconnect()
+
+exports["test map to undefined key"] = (test) ->
+    [c, ins, map, out] = setupComponent()
+    output = []
+    out.on "data", (data) ->
+        output.push data
+    out.once "disconnect", ->
+        test.same output, [{ undefined:1, b:2, c:3 }]
+        test.done()
+    map.send {a:undefined}
+    map.disconnect
+    ins.send o
+    ins.disconnect()
+
+exports["test map to false key"] = (test) ->
+    [c, ins, map, out] = setupComponent()
+    output = []
+    out.on "data", (data) ->
+        output.push data
+    out.once "disconnect", ->
+        test.same output, [{ false:1, b:2, c:3 }]
+        test.done()
+    map.send {a:false}
+    map.disconnect
+    ins.send o
+    ins.disconnect()
+
+