More testing of guarding methods

[jnyrup]

IMPORTANT

• The code complies with the Coding Guidelines for C#.
• The changes are covered by unit tests which follow the Arrange-Act-Assert syntax and the naming conventions such as is used in these tests.
• If the PR adds a feature or fixes a bug, please update the release notes with a functional description that explains what the change means to consumers of this library, which are published on the website.
• If the PR changes the public API the changes needs to be included by running AcceptApiChanges.ps1 or AcceptApiChanges.sh.
• If the PR affects the documentation, please include your changes in this pull request so the documentation will appear on the website.

Found that we didn't have fake Should overloads for DateTime[Offset]RangeAssertions since they don't have real Should overloads, but are always constructed from DateTime[Offset]Assertions.

I've also added code-coverage tests of guarding Equals methods right below Assertions_classes_override_equals which tests that bool Equals(object obj) is overridden.

[coveralls]

Pull Request Test Coverage Report for Build 2171994070

• 2 of 2 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.06%) to 95.229%

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Totals
Change from base Build 2171653108:	0.06%
Covered Lines:	8175
Relevant Lines:	8465

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💛 - Coveralls

[IT-VBFK]

Is this PR meant to be instead of #1889 ?

[jnyrup]

Is this PR meant to be instead of #1889 ?

Yes, Except the last test you wrote with null matching.

[IT-VBFK]

ok.. then I will remove this form the PR