Env var expansion feature in commandTests output assertions

Hi,

Would it be possible to get some env var expansion in output assertions of commandTests?

```
schemaVersion: 2.0.0

fileExistenceTests:
- name: 'Go Binary is present and executable'
path: '/usr/local/go/bin/go'
shouldExist: true
permissions: '-rwxr-xr-x'
isExecutableBy: 'root'
uid: 0
gid: 0

commandTests:
- name: 'Go version cmd to check go version'
command: 'go'
args: ['version']
expectedOutput: ['^go version go${GO_VERSION}.+$']
```

The associated container build spec is following one:

```
ARG BASE_VERSION
FROM docker.something.com/base-build:${BASE_VERSION}

USER root

ARG GOLANG_VERSION=1.21.3
ARG DEBIAN_FRONTEND=noninteractive

ENV GOPROXY https://artifactory.something.com/artifactory/go-remote/
ENV GONOSUMDB github.something.com/*
ENV PATH /usr/local/go/bin:${PATH}
ENV GOPATH /go
ENV GOLANG_VERSION=${GOLANG_VERSION}

RUN mkdir -p ${GOPATH} && \
curl "https://artifactory.something.com/artifactory/go-linux-remote/go${GOLANG_VERSION}.linux-amd64.tar.gz" --output /tmp/go.tar.gz && \
rm -rf /usr/local/go && tar -C /usr/local -xzf /tmp/go.tar.gz && \
rm /tmp/go.tar.gz

ARG GIT_SHA
ARG GIT_BRANCH

CMD ["/bin/bash"]
```

Thx for your help