Yep, dry runs with smaller, viable devices. The chemical and container are not as reported.
A lot of the time 'chemical spills' or 'incidents' are practice dry runs. It's a constant game of cat and mouse, most of the time, the cat catches the mouse, but sometimes they slip through and that's where attacks happen. It's terrifying how often these incidents happen with the public completely oblivious.
Source: family member in the CBRN.
I cannot, for obvious reasons, say any more than that.