Tests for next_occurrence break at certain times of day

[jemrobinson]

✅ Checklist

• I have searched open and closed issues for duplicates.
• This is a problem observed when deploying a Data Safe Haven.
• I can reproduce this with the latest version.
• I have read through the documentation.
• This isn't an open-ended question (open a discussion if it is).

💻 System information

• Operating System: macOS
• Data Safe Haven version: develop @ 9e5b72a

📦 Packages

List of packages

acme==2.6.0
annotated-types==0.6.0
appdirs==1.4.4
Arpeggio==2.0.2
attrs==23.2.0
azure-common==1.1.28
azure-core==1.30.1
azure-identity==1.16.0
azure-keyvault-certificates==4.8.0
azure-keyvault-keys==4.9.0
azure-keyvault-secrets==4.8.0
azure-mgmt-automation==1.0.0
azure-mgmt-compute==30.6.0
azure-mgmt-containerinstance==10.1.0
azure-mgmt-core==1.4.0
azure-mgmt-dns==8.1.0
azure-mgmt-keyvault==10.3.0
azure-mgmt-msi==7.0.0
azure-mgmt-network==25.3.0
azure-mgmt-rdbms==10.1.0
azure-mgmt-resource==23.0.1
azure-mgmt-storage==21.1.0
azure-storage-blob==12.19.1
azure-storage-file-datalake==12.14.0
azure-storage-file-share==12.15.0
certifi==2024.2.2
cffi==1.16.0
charset-normalizer==3.3.2
chevron==0.14.0
click==8.1.7
cryptography==42.0.6
-e git+ssh://git@github.com/jemrobinson/data-safe-haven.git@cb3d09511884bff82ab33b39e18b1db74dad7959#egg=data_safe_haven
dill==0.3.8
dnspython==2.4.2
fqdn==1.5.1
grpcio==1.60.1
idna==3.7
iniconfig==2.0.0
isodate==0.6.1
josepy==1.14.0
markdown-it-py==3.0.0
mdurl==0.1.2
msal==1.28.0
msal-extensions==1.1.0
msrest==0.7.1
oauthlib==3.2.2
packaging==24.0
parver==0.5
pluggy==1.5.0
portalocker==2.8.2
protobuf==4.25.3
psycopg==3.1.18
pulumi==3.115.0
pulumi_azure_native==2.39.0
pulumi_random==4.16.1
pycparser==2.22
pydantic==2.7.1
pydantic_core==2.18.2
Pygments==2.18.0
PyJWT==2.8.0
pyOpenSSL==24.1.0
pyRFC3339==1.1
pytest==8.2.0
pytest-asyncio==0.23.6
pytz==2023.4
PyYAML==6.0.1
requests==2.31.0
requests-oauthlib==2.0.0
rich==13.7.1
semver==2.13.0
setuptools==69.5.1
shellingham==1.5.4
simple-acme-dns==3.0.0
six==1.16.0
typer==0.12.3
typing_extensions==4.11.0
urllib3==2.2.1
validators==0.22.0
websocket-client==1.8.0

🚫 Describe the problem

At certain times of day next_occurrence can choose a datetime more than 1 day in the future, causing the tests to break.

🌳 Log messages

Relevant log messages

___________________ test_next_occurrence_is_within_next_day ____________________

    def test_next_occurrence_is_within_next_day():
        next_time = next_occurrence(5, 13, "Australia/Perth")
        dt_next_time = datetime.datetime.fromisoformat(next_time)
        dt_utc_now = datetime.datetime.now(datetime.UTC)
        assert dt_next_time > dt_utc_now
>       assert dt_next_time < dt_utc_now + datetime.timedelta(days=1)
E       AssertionError: assert datetime.datetime(2024, 5, 17, 21, 13, tzinfo=datetime.timezone.utc) < (datetime.datetime(2024, 5, 16, 16, 52, 28, 540053, tzinfo=datetime.timezone.utc) + datetime.timedelta(days=1))
E        +  where datetime.timedelta(days=1) = <class 'datetime.timedelta'>(days=1)
E        +    where <class 'datetime.timedelta'> = datetime.timedelta

tests/functions/test_strings.py:16: AssertionError

♻️ To reproduce

Run hatch run test:test at around 16:15 UTC.