If you’re using a recent version of Cargo (0.5.0 or higher), you can use the `cargo install` command:

Cargo will clone the repository to a temporary directory, build it there and place the `exa` binary to: `$HOME/.cargo` (and can be overridden by setting the `--root` option).

exa uses [Vagrant][] to configure virtual machines for testing.

Programs such as exa that are basically interfaces to the system are [notoriously difficult to test][testing]. Although the internal components have unit tests, it’s impossible to do a complete end-to-end test without mandating the current user’s name, the time zone, the locale, and directory structure to test. (And yes, these tests are worth doing. I have missed an edge case on more than one occasion.)

The initial attempt to solve the problem was just to create a directory of “awkward” test cases, run exa on it, and make sure it produced the correct output. But even this output would change if, say, the user’s locale formats dates in a different way. These can be mocked inside the code, but at the cost of making that code more complicated to read and understand.

An alternative solution is to fake *everything*: create a virtual machine with a known state and run the tests on *that*. This is what Vagrant does. Although it takes a while to download and set up, it gives everyone the same development environment to test for any obvious regressions.

[Vagrant]: https://www.vagrantup.com/docs/why-vagrant/

[testing]: https://eev.ee/blog/2016/08/22/testing-for-people-who-hate-testing/#troublesome-cases

First, initialise the VM:

host$ vagrant up

The first command downloads the virtual machine image, and then runs our provisioning script, which installs Rust, exa’s dependencies, configures the environment, and generates some awkward files and folders to use as test cases. This takes some time, but it does write to output occasionally. Once this is done, you can SSH in, and build and test:

host$ vagrant ssh

vm$ cd /vagrant

vm$ cargo build

vm$ ./xtests/run

All the tests passed!

Of course, the drawback of having a standard development environment is that you stop noticing bugs that occur outside of it. For this reason, Vagrant isn’t a *necessary* development step — it’s there if you’d like to use it, but exa still gets used and tested on other platforms. It can still be built and compiled on any target triple that it supports, VM or no VM, with `cargo build` and `cargo test`.

Vagrant.configure("2") do |config|

config.vm.provider "virtualbox" do |v|

v.memory = 1024

v.cpus = 1

end

config.vm.box = "debian/contrib-jessie64"

config.vm.hostname = "exa"

# Install the dependencies needed for exa to build.

config.vm.provision :shell, privileged: true, inline:

%[apt-get install -y git cmake libgit2-dev libssh2-1-dev curl attr]

# Guarantee that the timezone is UTC -- some of the tests

# depend on this (for now).

config.vm.provision :shell, privileged: true, inline:

%[timedatectl set-timezone UTC]

# Install Rust.

# This is done as vagrant, not root, because it’s vagrant

# who actually uses it. Sent to /dev/null because the progress

# bar produces a lot of output.

config.vm.provision :shell, privileged: false, inline:

%[hash rustc &>/dev/null || curl -sSf https://static.rust-lang.org/rustup.sh | sh &> /dev/null]

# Use a different ‘target’ directory on the VM than on the host.

# By default it just uses the one in /vagrant/target, which can

# cause problems if it has different permissions than the other

# directories, or contains object files compiled for the host.

config.vm.provision :shell, privileged: false, inline:

%[echo "export CARGO_TARGET_DIR=/home/vagrant/target" >> ~/.bashrc]

# Test that wide columns work with a really long username.

# The benefit of Vagrant is that we don’t need to set this up

# on the *actual* system!

longuser = "antidisestablishmentarienism"

config.vm.provision :shell, privileged: true, inline:

%[id -u #{longuser} &>/dev/null || useradd #{longuser}]

test_dir = "/home/vagrant/testcases"

invalid_uid = 666

invalid_gid = 616

some_date = "201601011234.56" # 1st January 2016, 12:34:56

# Delete old testcases if they exist already.

# This needs root because the generator does some sudo-ing.

config.vm.provision :shell, privileged: true, inline:

%[rm -rfv #{test_dir}]

# Generate our awkward testcases.

config.vm.provision :shell, privileged: false, inline:

%[mkdir #{test_dir}]

# Awkward file size testcases.

config.vm.provision :shell, privileged: false, inline: <<-EOF

# Awkward symlink testcases.

config.vm.provision :shell, privileged: false, inline: <<-EOF

# Awkward passwd testcases.

# sudo is needed for these because we technically aren’t a member

# of the groups (because they don’t exist), and chown and chgrp

# are smart enough to disallow it!

config.vm.provision :shell, privileged: false, inline: <<-EOF

# Awkward permission testcases.

config.vm.provision :shell, privileged: false, inline: <<-EOF

# Awkward extended attribute testcases.

config.vm.provision :shell, privileged: false, inline: <<-EOF