Add test for transition.call.

test/core/transition-test-call.js

@@ -0,0 +1,33 @@
+require("../env");
+require("../../d3");
+
+var assert = require("assert");
+
+module.exports = {
+  topic: function() {
+    return d3.select("body").append("div").transition();
+  },
+  "calls the function once": function(transition) {
+    var count = 0;
+    transition.call(function() { ++count; });
+    assert.equal(count, 1);
+  },
+  "passes any optional arguments": function(transition) {
+    var abc;
+    transition.call(function(selection, a, b, c) { abc = [a, b, c]; }, "a", "b", "c");
+    assert.deepEqual(abc, ["a", "b", "c"]);
+  },
+  "passes the transition as the first argument": function(transition) {
+    var t;
+    transition.call(function(x) { t = x; });
+    assert.isTrue(t === transition);
+  },
+  "uses the transition as the context": function(transition) {
+    var t;
+    transition.call(function() { t = this; });
+    assert.isTrue(t === transition);
+  },
+  "returns the current transition": function(transition) {
+    assert.isTrue(transition.call(function() {}) === transition);
+  }
+};

test/core/transition-test.js

@@ -39,9 +39,9 @@ suite.addBatch({
   "duration": require("./transition-test-duration"),
 
   // Control
-  "each": require("./transition-test-each")
+  "each": require("./transition-test-each"),
+  "call": require("./transition-test-call")
   // tween
-  // call
 
 });