🧪 Add snapshot testing for needs data

[chrisjsewell]

Previously, the validity of needs data was tested by asserting for only specific keys and values.
This PR adds snapshot testing, with https://github.com/tophat/syrupy, to more fully capture the generated data.
This should help to better identify any regressions caused by future changes (such as in #1018).

[danwos]

That's a great idea, using snapshot for this.

Is the snapshot-file taken automatically based on the test-file name?
Can the exact name of the snapshot be configured in the pytest?
I see use cases, where the snapshot may differ for specific tests in the same test-file.
Maybe this can also be documented in contributing in 1-2 lines.

However, approved 👍

[chrisjsewell]

Is the snapshot-file taken automatically based on the test-file name?

Yes

Can the exact name of the snapshot be configured in the pytest?

I don't believe so

I see use cases, where the snapshot may differ for specific tests in the same test-file.

I think maybe you are misunderstanding?
A snapshot file can hold multiple snapshots, for a single test file; for each test and even multiple per test (https://github.com/tophat/syrupy#name)