Testing: Adapt "Testcontainers" implementation to unittest

[amotl]

Introduction

Over here, we reported about the state of the "Testcontainers for Python" implementation, for supporting application testing with CrateDB.

• Testing: Improve "Testcontainers for Python" implementation #57

About

At the issue referenced above, we will need to resolve this backlog item, in order to make the test layer usable for applications/libraries which are using Python's unittest module for testing.

While a pytest-based wrapper adapter around the "Testcontainers" implementation is nice, the projects crate-python and crash are using Python's builtin unittest module. Can we also grow a unittest-based wrapper adapter, to be reusable by both downstream projects?

Task

Use testing infrastructure from cratedb_toolkit.testing.testcontainers.cratedb and maybe cratedb_toolkit.tests.conftest.CrateDBFixture, and adapt that to unittest instead of using the pytest-specific details.

First Candidate

As a first candidate to apply this adapter, we identified the crash terminal program. This other ticket there outlines how/where to use the unittest-based adapter instead of the previous one.

• Use CrateDB test layer based on "Testcontainers", in order to improve platform coverage crate/crash#402