compile mono c# solution on circle ci

circle.yml

dependencies:
    cache_directories:
        - packages
        - "~/.apt-cache"
    pre:
        # https://discuss.circleci.com/t/add-ability-to-cache-apt-get-programs/598/4
        - sudo rm -rf /var/cache/apt/archives && sudo ln -s ~/.apt-cache /var/cache/apt/archives && mkdir -p ~/.apt-cache/partial
        - mkdir -p packages

    override:
        # http://www.mono-project.com/docs/getting-started/install/linux/
        - sudo apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv-keys 3FA7E0328081BFF6A14DA29AA6A19B38D3D831EF
        - echo "deb http://download.mono-project.com/repo/debian wheezy main" | sudo tee /etc/apt/sources.list.d/mono-xamarin.list
        - sudo apt-get update
        # http://www.mono-project.com/docs/getting-started/install/linux/#usage
        - sudo apt-get install -y mono-complete
        - sudo apt-get install -y referenceassemblies-pcl
        - sudo apt-get install -y ca-certificates-mono
        - sudo apt-get install -y nunit-console

        - cd packages; wget --no-check-certificate https://dist.nuget.org/win-x86-commandline/latest/nuget.exe
        - mono packages/nuget.exe restore

test:
    override:
        - xbuild
        - nunit-console <test project name>/bin/Debug/<test project name>.dll