Ensures expectations involving multiple assertions can be cleared

[dennisdoomen]

Introduces a ClearExpectation to undo the expectation that is associated with multiple assertions using WithExpectation. Without it, it is possible that this expectation gets appended to any successive assertions.

Fixes #918

[jnyrup]

I'm not sure what the functional consequences are?

[jnyrup]

🤔 As IAssertionScope doesn't have all the public members of AssertionScope this is a breaking change

[dennisdoomen]

I'm not sure. The members of IAssertionScope are only used in chaining scenarios. I've included a couple of them, but not all. Any strong opinions?

[jnyrup]

I haven't tried to invoke AssertionScope-only members myself, I just looked for changes that could break the public API.

[dennisdoomen]

Normally, you're directly using the AssertionScope in a using block. The interface is only used for those complex chaining purposes. In the last commit, I've added almost all of them to the interface, just to be sure.

[jnyrup]

But no, I don't have any strong opinions, except trying to avoid breaking changes.

Just as a note: the remaining differences between AssertionScope and IAssertionScope are:

public string Context { get; set; }
public void AddPreFormattedFailure(string formattedFailureMessage);
void AddNonReportable(string key, object value);
void AddReportable(string key, string value);
T Get<T>(string key);

[dennisdoomen]

Yes, I know. These are very specific things, mostly only used by BeEquivalentTo.

[dennisdoomen]

So? Approved?

[jnyrup]

Would these changes benefit from any tests exercising the code?

[dennisdoomen]

I'm in doubt. I would have to check whether the failure doesn't contain anything else. Not sure if it's worth though. I'll check when I continue with #911.