integration-test: add test scenarios

[ahmetb]

The integration tests use bats to run the scenarios as bash scripts.

To test the extension handler functionality, we simply:

• build a Docker image using test.Dockerfile
  • copy some files from make it look like a/var/lib/waagent` directory
  • copy extension binary into the container
• remove the test container if it exists
• create a Docker container (name: test) from image
  • specify which handler subcommand will be invoked (e.g. fake-waagent install)
• push .settings file and certificate/private key to the container (.crt, .prv)
  • do other things on the container that we need to craft the environment
• start the container
• collect the output from the command execution
• validate using the following:
  • check status code
  • validate output of the command
  • docker diff test to validate file changes in the container
  • copy files out of container and validate their contents

[ahmetb]

Tests are expected to fail as this is not rebased on top of #31. I still have not plugged these tests in travis-ci (I'm not sure it'll work as integration tests require a docker daemon). That'll be another PR.

[ahmetb]

Running these tests looks like this

bats integration-test/test
 ✓ meta: docker is installed
 ✓ meta: can build the test container image
 ✓ meta: can start the test container
 ✓ meta: can create vm private/public keys
 ✓ meta: encrypt a protected settings
 ✓ meta: can create a .settings json with public/protected config
 ✓ meta: can create a temporary file
 ✓ handler command: install - creates the data dir
 ✓ handler command: enable - can process empty settings, but fails
 ✓ handler command: enable - validates json schema
 ✓ handler command: enable - captures stdout/stderr into file
 ✓ handler command: enable - doesn't process the same sequence number again
 ✓ handler command: enable - parses protected settings
 ✓ handler command: enable - downloads files
 ✓ handler command: uninstall - deletes the data dir

15 tests, 0 failures

[boumenot]

Why is this scoped to this method?

[ahmetb]

I believe setting -e globally has issues with bats sstephenson/bats#171

[boumenot]

LGTM.