Just did a sequential run (to get some better measurements), and this is an excerpt of the things happening in the PostgreSQL instance inside the Docker container, for creating and dropping the databases:
08:25:37.114 UTC [1456] LOG: statement: CREATE DATABASE "test_1675239937111796557" WITH template = test_template
[noise]
08:25:48.002 UTC [1486] LOG: statement: DROP DATABASE "test_1675239947937354435"
Start time of first test:
2023-02-01 08:25:03.633 UTC
Finish time of last test:
2023-02-01 08:26:13.861 UTC
82 tests, or 0.856 seconds per test (sequentially).
In parallel, we take 6.941 seconds for 82 tests, or 0.085 seconds per test.
We apply the overall same strategy (individual DB for each test created from a template).
Our whole test suite (integration + unit tests) takes ~80 seconds to run for ~800 integration tests (each with their own DB) and 300 unit tests. And that's on my dev laptop (T14s, cpu: i7-1185G7) without much optimization (mainly fsync = off in postgresql.conf).
In fact, I just ran a quick test, and just putting the DB on a tmpfs cuts that time to ~40 seconds.
So overall 0.1 to 0.05 second per test on average, same ballpark as parent (and it's kind of an over estimation actually since we have a dozen or so of slow tests taking 5 to 10 seconds).
Finish time of last test: 2023-02-01 08:26:13.861 UTC
82 tests, or 0.856 seconds per test (sequentially).
In parallel, we take 6.941 seconds for 82 tests, or 0.085 seconds per test.