Let $f:X\to Y$ be a morphism of finite type between finite type schemes $X,Y$ over a field $k$. By the infinitesimal criterion for (formal) smoothness, f is smooth if given a commutative diagram 

$$\begin{array}[c]{ccc}
T& {\rightarrow}&X\\
\downarrow &&\downarrow\scriptstyle{f}\\
T'& {\rightarrow}&Y
\end{array}$$

where $T⊂T′$ is a first order thickening of affine schemes, there exists a morphism $T'\to X$ that fits in the above diagram. 

**Question**: Is it true that is enough to check smoothness using the above criterion, but only restricting to all $T⊂T′$ where $T'$ is a trivial extension of $T$? That is $T'=T\times_{Spec k} Spec\ k[\epsilon]$ where $\epsilon^2=0$.