Fix test and add symmetric test for append.

test/selection/append-test.js

@@ -94,6 +94,24 @@ suite.addBatch({
   }
 });
 
+suite.addBatch({
+  "enter-append": {
+    topic: load("selection/selection").document(),
+    "on a page with existing elements": {
+      topic: function(d3) {
+        var body = d3.select("body");
+        body.selectAll("div").data(["apple", "orange"]).enter().append("div");
+        return body;
+      },
+      "appends to the end of the parent": function(body) {
+        var data = ["peach", "apple", "banana", "orange", "apricot"];
+        body.selectAll("div").data(data, String).enter().append("div");
+        assert.deepEqual(body.selectAll("div").data(), ["apple", "orange", "peach", "banana", "apricot"]);
+      }
+    }
+  }
+});
+
 suite.addBatch({
   "selectAll(div).data(…).enter()": {
     topic: load("selection/selection").document(),

test/selection/insert-test.js

@@ -111,7 +111,7 @@ suite.addBatch({
 });
 
 suite.addBatch({
-  "enter insert": {
+  "enter-insert": {
     topic: load("selection/selection").document(),
     "on a page with existing elements": {
       topic: function(d3) {
@@ -121,7 +121,7 @@ suite.addBatch({
       },
       "inserts before the following updating sibling": function(body) {
         var data = ["peach", "apple", "banana", "orange", "apricot"];
-        body.selectAll("div").data(data).enter().insert("div");
+        body.selectAll("div").data(data, String).enter().insert("div");
         assert.deepEqual(body.selectAll("div").data(), data);
       }
     }