Add test for transition.tween.

test/core/transition-test-tween.js

@@ -0,0 +1,71 @@
+require("../env");
+require("../../d3");
+
+var assert = require("assert");
+
+module.exports = {
+  topic: function() {
+    var cb = this.callback,
+        dd = [],
+        ii = [],
+        tt = [],
+        fails = 0;
+
+    var s = d3.select("body").append("div").selectAll("div")
+        .data(["red", "green"])
+      .enter().append("div")
+        .text(function(d) { return d3.rgb(d)+""; });
+
+    var t = s.transition()
+        .tween("text", function() { ++fails; })
+        .tween("text", tween);
+
+    function tween(d, i) {
+      dd.push(d);
+      ii.push(i);
+      if (tt.push(this) >= 2) cb(null, {
+        selection: s,
+        transition: t,
+        data: dd,
+        index: ii,
+        context: tt,
+        fails: fails
+      });
+      return i && function(t) {
+        this.textContent = d3.hsl(230, 0.5, t) + "";
+      };
+    }
+  },
+
+  // The order here is a bit brittle: because the transition has zero delay,
+  // it's invoking the start event immediately for all nodes, rather than
+  // pushing each node onto the timer queue (which would reverse the order of
+  // callbacks). The order in which tweens are invoked is undefined, so perhaps
+  // we should sort the expected and actual values before comparing.
+
+  "defines the corresponding tween": function(result) {
+    assert.typeOf(result.transition.tween("text"), "function");
+  },
+  "the last tween takes precedence": function(result) {
+    assert.equal(result.fails, 0);
+  },
+  "invokes the tween function": function(result) {
+    assert.deepEqual(result.data, ["red", "green"], "expected data, got {actual}");
+    assert.deepEqual(result.index, [0, 1], "expected data, got {actual}");
+    assert.domEqual(result.context[0], result.selection[0][0], "expected this, got {actual}");
+    assert.domEqual(result.context[1], result.selection[0][1], "expected this, got {actual}");
+  },
+
+  "end": {
+    topic: function(result) {
+      var cb = this.callback;
+      result.transition.each("end", function(d, i) { if (i >= 1) cb(null, result); });
+    },
+    "uses the returned tweener": function(result) {
+      assert.equal(result.selection[0][1].textContent, "hsl(230,50%,100%)");
+    },
+    "does nothing if the tweener is falsey": function(result) {
+      assert.equal(result.selection[0][0].textContent, "#ff0000");
+    }
+  }
+};

test/core/transition-test.js

@@ -42,8 +42,8 @@ suite.addBatch({
 
   // Control
   "each": require("./transition-test-each"),
-  "call": require("./transition-test-call")
-  // tween
+  "call": require("./transition-test-call"),
+  "tween": require("./transition-test-tween")
 
 });