'main': Add test for #548
'main': Add test for #548

Closes #548

zsh-users/zsh-syntax-highlighting,P71/zsh-syntax-highlighting,zsh-users/zsh-syntax-highlighting,x-way/zsh-syntax-highlighting,phy1729/zsh-syntax-highlighting,P71/zsh-syntax-highlighting,x-way/zsh-syntax-highlighting,phy1729/zsh-syntax-highlighting