I have to define a new environment doing something like that.

```
\documentclass[12pt]{article}
\usepackage{tcolorbox,empheq}
\begin{document}
\begin{tcolorbox}
\begin{empheq}{align}
a=b
\end{empheq}
\end{tcolorbox}
\end{document}

```

[![screenshot](https://i.stack.imgur.com/y1LD4.png)](https://i.stack.imgur.com/y1LD4.png)

This code works fine, but if I try something like testa or testb, I get errors.

```
\documentclass[12pt]{article}
\usepackage{tcolorbox,empheq}

\newenvironment{testa}{\tcolorbox\empheq{align}}{\endempheq\endtcolorbox}
\newenvironment{testb}{\tcolorbox\setkeys{EmphEqEnv}{align}\EmphEqMainEnv}{\endEmphEqMainEnv\endtcolorbox}

\begin{document}
\begin{testa}
a=b
\end{testa}
\end{document}

```

Is there a solution ?