unit tests

test/inDelta.js

@@ -1,10 +1,26 @@
 var tape = require("tape");
 
-tape.Test.prototype.inDelta = function(actual, expected) {
-  this._assert(expected - 1e-6 < actual && actual < expected + 1e-6, {
-    message: "should be in delta",
+tape.Test.prototype.inDelta = function(actual, expected, delta) {
+  delta = delta || 1e-6;
+  this._assert(inDelta(actual, expected, delta), {
+    message: "should be in delta " + delta,
     operator: "inDelta",
     actual: actual,
     expected: expected
   });
 };
+
+function inDelta(actual, expected, delta) {
+  return (Array.isArray(expected) ? inDeltaArray : inDeltaNumber)(actual, expected, delta);
+}
+
+function inDeltaArray(actual, expected, delta) {
+  var n = expected.length, i = -1;
+  if (actual.length !== n) return false;
+  while (++i < n) if (!inDelta(actual[i], expected[i], delta)) return false;
+  return true;
+}
+
+function inDeltaNumber(actual, expected, delta) {
+  return actual >= expected - delta && actual <= expected + delta;
+}

test/zoom-test.js

@@ -5,3 +5,33 @@ tape("interpolateZoom(a, b) handles nearly-coincident points", function(test) {
   test.deepEqual(interpolate.interpolateZoom([324.68721096803614, 59.43501602433761, 1.8827137399562621], [324.6872108946794, 59.43501601062763, 7.399052110984391])(0.5), [324.68721093135775, 59.43501601748262, 3.7323313186268305]);
   test.end();
 });
+
+tape("interpolateZoom returns the expected duration", function(test) {
+  test.inDelta(interpolate.interpolateZoom([0, 0, 1], [0, 0, 1.1]).duration, 67, 1);
+  test.inDelta(interpolate.interpolateZoom([0, 0, 1], [0, 0, 2]).duration, 490, 1);
+  test.inDelta(interpolate.interpolateZoom([0, 0, 1], [10, 0, 8]).duration, 2872.5, 1);
+  test.end();
+});
+
+tape("interpolateZoom parameter rho() defaults to sqrt(2)", function(test) {
+  test.inDelta(
+    interpolate.interpolateZoom.rho(Math.sqrt(2))([0,0,1], [10, 10, 5])(0.5),
+    interpolate.interpolateZoom([0,0,1], [10, 10, 5])(0.5)
+  );
+  test.inDelta(interpolate.interpolateZoom.rho(), Math.sqrt(2));
+  test.end();
+});
+
+tape("interpolateZoom.rho(0) is (almost) linear", function(test) {
+  const interp = interpolate.interpolateZoom.rho(0)([0, 0, 1], [10, 0, 8]);
+  test.inDelta(interp(0.5), [1.111, 0, Math.sqrt(8)], 1e-3);
+  test.equal(Math.round(interp.duration), 1470);
+  test.end();
+});
+
+tape("interpolateZoom parameter rho(2) has a high curvature and takes more time", function(test) {
+  const interp = interpolate.interpolateZoom.rho(2)([0, 0, 1], [10, 0, 8]);
+  test.inDelta(interp(0.5), [1.111, 0, 12.885], 1e-3);
+  test.equal(Math.round(interp.duration), 3775);
+  test.end();
+});