Testing UBOS apps

About webapptest

It’s very important that apps on UBOS deploy correctly, undeploy cleanly, and that their data can be reliably backed up, restored, and migrated when your app moves to a new version. We do not ever want to ask a user to “fix the app installation” manually if we can help it.

To aid in testing this, we use a test tool called webapptest (webapptest source is here), which has been written specifically for this purpose. webapptest is not a regular application testing tool; it is not intended to find out whether, say, your app runs nicely in Internet Explorer. Instead, it focuses on testing installation, uninstallation, backup and restore; something typical testing tools don’t focus on.

Example: Testing Glad-I-Was-Here locally

To test the Glad-I-Was-Here toy application with all the default settings on a device running UBOS, execute:

> webapptest run

(see here)

This will go through a series of steps deploying gladiwashere on your local device, interacting with the app by filling out a guestbook entry, backing up the app data, undeploying the app, re-deploying and restoring from backup.

The exact steps depend on the test plan you are using. To see available test plans, execute:

> webapptest listtestplans
backup-all-states  - Creates a local backup file for each State.
default            - Walks through all States and Transitions, and attempts to backup and restore each State.
deploy-only        - Only tests whether the application can be installed.
deploy-update      - Tests whether the application can be installed and updated.
redeploy           - Tests that the application can be re-deployed after install at different hostnames.
restore-all-states - Restores from a local backup file for each State, and tests upgrade.
simple             - Walks through all States and Transitions in sequence.
well-known         - Walks twice through all States and Transitions in sequence, checking well-known site fields only.

To employ a test plan that is not the default, specify --testplan <name> as an argument to webapptest.

Alternate scaffolds

webapptest also knows the notion of a scaffold. To show the available scaffolds, execute:

> webapptest listscaffolds
container - A scaffold that runs tests on the local machine in a Linux container.
here      - A trivial scaffold that runs tests on the local machine without any insulation.
ssh       - A scaffold that runs tests on the remote machine that is already set up, and accessible via ssh.
v-box     - A scaffold that runs tests on the local machine in a VirtualBox virtual machine.

If using webapptest with the here scaffold, webapptest deploys the to-be-tested app on the local device (which needs to run UBOS). This is also the default.

By using the ssh scaffold, the to-be-tested app can be tested on a remote UBOS device over ssh. This is particularly useful for cross-platform testing.

The v-box scaffold sets up and tears down an entire UBOS virtual machine for the test. This is only available on x86_64.

Finally, the container scaffold creates a Linux container into which UBOS and the to-be-tested app will be installed, using systemd-nspawn.

Some of these scaffolds need parameters (e.g. the hostname of the ssh host or the image to boot from), which are specified by appending them to the name of the scaffold like this:

> webapptest run --scaffold container:directory=/build/my-ubos-image-dir

Test description

To define a test for webapptest, follow the example in

The essence of the test description is a series of states and transitions between them. The states are states (with different data) that the application can be in. In GladIWasHereTest1, those are:

  • virgin: the app has just been deployed, and nobody has filled out a guestbook entry yet
  • comment-posted: a single comment has been posted

Obviously, depending on the application, many more states can be defined.

For each of these states, a script is run that tests that the application is indeed in this state.

Transitions capture instructions for how webapptest can move the application from one state to another. Here, we have only one, called post-comment, which contains the code to post a guestbook entry.

The essence of the test are the getMustContain and similar statements in the states. getMustContain will perform an HTTP GET operation on the provided URL (relative to the location at which the app was installed), and make sure that the received content contains a certain pattern. If not, it will print the provided error message.

The full API is here.