The title says it all. Spawning a Test Tube produces what appears to be an empty tube, however the truth is, the liquid within is not drawing over surfaces, unless you hover over the tube while holding Q. The Tube and its liquid are not colorable either, despite the fact the throwable one does have multiple colors.
Spawn the Tube
To see a strange colorable liquid within.
No liquid visible in the tube unless hovered over in the Q menu.
Additionally, if we could get a slider to adjust how high the liquid is in the tube, it would be great to add some finer details to a Halloween set.