diff -r efd9c589177a -r c0b4a8b5a012 toolkit/javascript/d3/test/layout/histogram-test.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/toolkit/javascript/d3/test/layout/histogram-test.js	Thu Apr 10 14:20:23 2014 +0200
@@ -0,0 +1,91 @@
+require("../env");
+require("../../d3");
+require("../../d3.layout");
+
+var vows = require("vows"),
+    assert = require("assert");
+
+var suite = vows.describe("d3.layout.histogram");
+
+suite.addBatch({
+  "histogram": {
+    topic: function() {
+      return d3.layout.histogram;
+    },
+    "defaults to frequencies": function(histogram) {
+      var h = histogram();
+      assert.deepEqual(h([0,0,0,1,2,2]).map(elements), [[0, 0, 0], [], [1], [2, 2]]);
+    },
+    "each bin contains the matching source elements": function(histogram) {
+      var h = histogram();
+      assert.deepEqual(h([0,0,0,1,2,2]).map(elements), [[0, 0, 0], [], [1], [2, 2]]);
+    },
+    "each bin also has defined x, y and dx properties": function(histogram) {
+      var h = histogram();
+      assert.deepEqual(h([0,0,0,1,2,2]).map(metadata), [
+        {x:   0, y: 3, dx: 0.5},
+        {x: 0.5, y: 0, dx: 0.5},
+        {x:   1, y: 1, dx: 0.5},
+        {x: 1.5, y: 2, dx: 0.5}
+      ]);
+    },
+    "can output frequencies": function(histogram) {
+      var h = histogram().frequency(true);
+      assert.deepEqual(h([0,0,0,1,2,2]).map(metadata), [
+        {x:   0, y: 3, dx: 0.5},
+        {x: 0.5, y: 0, dx: 0.5},
+        {x:   1, y: 1, dx: 0.5},
+        {x: 1.5, y: 2, dx: 0.5}
+      ]);
+    },
+    "can output probabilities": function(histogram) {
+      var h = histogram().frequency(false);
+      assert.deepEqual(h([0,0,0,1,2,2]).map(metadata), [
+        {x:   0, y: 3/6, dx: 0.5},
+        {x: 0.5, y:   0, dx: 0.5},
+        {x:   1, y: 1/6, dx: 0.5},
+        {x: 1.5, y: 2/6, dx: 0.5}
+      ]);
+    },
+    "can specify number of bins": function(histogram) {
+      var h = histogram().bins(2);
+      assert.deepEqual(h([0,0,0,1,2,2]).map(elements), [
+        [0, 0, 0],
+        [1, 2, 2]
+      ]);
+      assert.deepEqual(h([0,0,0,1,2,2]).map(metadata), [
+        {x: 0, y: 3, dx: 1},
+        {x: 1, y: 3, dx: 1}
+      ]);
+    },
+    "can specify bin thresholds": function(histogram) {
+      var h = histogram().bins([0,1,2,3]);
+      assert.deepEqual(h([0,0,0,1,2,2]).map(elements), [
+        [0, 0, 0],
+        [1],
+        [2, 2]
+      ]);
+      assert.deepEqual(h([0,0,0,1,2,2]).map(metadata), [
+        {x: 0, y: 3, dx: 1},
+        {x: 1, y: 1, dx: 1},
+        {x: 2, y: 2, dx: 1}
+      ]);
+    }
+  }
+});
+
+function elements(bin) {
+  var array = [], i = -1, n = bin.length;
+  while (++i < n) array.push(bin[i]);
+  return array;
+}
+
+function metadata(bin) {
+  var metadata = {};
+  if ("x" in bin) metadata.x = bin.x;
+  if ("y" in bin) metadata.y = bin.y;
+  if ("dx" in bin) metadata.dx = bin.dx;
+  return metadata;
+}
+
+suite.export(module);