Metadata test full serialization cycle

[MVrachev]

Description of the changes being introduced by the pull request:

Replace the usage of Metadata.to_dict inside
test_valid_metadata_serialization and instead use Metadata.to_bytes()
in order to test that the full serialization cycle is working as
expected:
Metadata.from_bytes -> Metadata.to_bytes

Raised from Jussi's comment: #1809 (comment)

Signed-off-by: Martin Vrachev [email protected]

Please verify and check that the pull request fulfills the following
requirements:

• The code follows the Code Style Guidelines
• Tests have been added for the bug fix or new feature
• Docs have been added for the bug fix or new feature

[coveralls]

Pull Request Test Coverage Report for Build 1833914149

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 98.347%

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Totals
Change from base Build 1828868126:	0.0%
Covered Lines:	1121
Relevant Lines:	1137

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💛 - Coveralls

[jku]

Neither option here is great IMO: we either don't test the full serialization cycle. or we end up hard coding the specific json options in the test (and then the test still won't notice if json module somehow changes how it works).

This isn't a complaint on the patch as such: I'm just saying we need to admit that this type of testing does not work well with complete metadata files and the complete serialization cycle: generating metadata (and verifying the results do not change) is a better approach for that: #1806

Anyway, looks good to me, but let's not try to force a round peg into a square hole any more than this (unless there's some new squaring-a-circle ideas of course)