TestPyQgsPostgresProvider.testGeneratedColumns is not idempotent

[strk]

What is the bug or the crash?

Running this twice:

python3 tests/src/python/test_provider_postgres.py TestPyQgsPostgresProvider.testGeneratedColumns

Will pass the first time but fail the second time.
I think tests should be idempotent instead

NOTE: the python3 call should be made after setting proper env variables as documented in tests/README

Steps to reproduce the issue

from the build tree:

export QGIS_PREFIX_PATH=output PYTHONPATH=output/python:$PYTHONPATH
python3 tests/src/python/test_provider_postgres.py  TestPyQgsPostgresProvider.testGeneratedColumns
python3 tests/src/python/test_provider_postgres.py  TestPyQgsPostgresProvider.testGeneratedColumns

Versions

current master

Supported QGIS version

• I'm running a supported QGIS version according to the roadmap.

New profile

• I tried with a new QGIS profile

Additional context

No response

[strk]

The error on second run is:

  Provider errors:
      PostGIS error while adding features: ERROR:  duplicate key value violates unique constraint "generated_columns_pkey"
    DETAIL:  Key (pk)=(2) already exists.
    
F
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FAIL: testGeneratedColumns (__main__.TestPyQgsPostgresProvider)
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Traceback (most recent call last):
  File "/home/src/qgis/qgis/src/master/tests/src/python/providertestbase.py", line 1192, in testGeneratedColumns
    self.assertFalse(QgsVectorLayerUtils.fieldIsEditable(vl, 0, feature))
AssertionError: True is not false

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