JavaScript test descriptions are wrong (and also grammatically incorrect):
Test.assertEquals(buildOneTwoThree().data, 1, "First node should should have 1 as data.");
Test.assertEquals(buildOneTwoThree().next.data, 2, "First node should should have 1 as data.");
Test.assertEquals(buildOneTwoThree().next.next.data, 3, "Second node should should have 2 as data.");
Test.assertEquals(buildOneTwoThree().next.next.next, null, "Third node should should have 3 as data.");

Problems:

1. Too many "should"'s;
2. Second description is a copy of the first description;
3. Descriptions after second one are "shifted" by 1 and are, therefore, wrong.

All of this is very misleading.

Yep, really annoying, got bitten by it just now.