[CI/CD] Integration-Tests / Samples execution/generation on CI env

[hypery2k]

Description

Currently to me the testing approach seems a little bit weired:

• The generated samples are checked in
• There are scripts within bin which use latest version
• Not all samples are executed

Swagger-codegen version

latest 3.0.0 branch

Swagger declaration file content or url

N/A

Command line used for generation

N/A

Steps to reproduce

 mvn -q --batch-mode verify -Psamples

;)

Related issues/PRs

e.g. this error would have been found before releasing: #9822

Suggest a fix/enhancement

1. I think the samples folder should just hold the pom.xml
2. For the rest the scripts should run on CI
3. All samples should be executed on travis

[kaibra]

I recently spend some thoughts and time on this topic.
I came up with a different solution for integration tests which is based on testcontainers, it works like this:

• All integration-tests are part of the test-code base (Java)
• An integration Test generates sources based on some test-data (e.g. petstore, ...) into a temporary directory
• After this a testcontainer (https://www.testcontainers.org/) is started
• the temporary directory is mounted into the container as well as caches for dependencies (e.g. m2 cache)
• within the container itself the generated code is compiled and tests are run

Benefits of this:

• you can use a docker container of your choice for each language supported. the environment is isolated / separated from others
• propper test-results can be written (junit)
• run integration tests easily within your IDE without having to understand a complex workflow (git commit + push / samples dir / mvn profile / pom module wrapper around others languages / ....)
• tests can also be parallelized

I put a small example on how this can be done into a repo: https://github.com/kaibra/swagger-codegen-integration/blob/master/src/test/java/de/kaibra/swaggercodegenintegration/languages/java/JavaCodegenITest.java

@HugoMario what do you think about this?