n() {
    var v0 = goog.vec.vec2d.setFromValues(goog.vec.vec2d.create(), 1, 2);
    var v1 = goog.vec.vec2d.setFromValues(goog.vec.vec2d.create(), 1, 2);
    var dirVec = goog.vec.vec2d.setFromValues(goog.vec.vec2d.create(), 4, 5);
    goog.vec.vec2d.direction(v0, v1, dirVec);
    assertElementsEquals([0, 0], dirVec);
    goog.vec.vec2d.setFromValues(v0, 0, 0);
    goog.vec.vec2d.setFromValues(v1, 1, 0);
    goog.vec.vec2d.direction(v0, v1, dirVec);
    assertElementsEquals([1, 0], dirVec);
    goog.vec.vec