Extending Assertions

[jesuslpm]

I have this method to assert that a record is valid:

public static async Task ValidRecord(RedisLockRecord record, string resourceId, TimeSpan timeToLive, string lockedByDescription)
{

	await Assert.That(record).IsNotNull();
	TimeSpan maxDelay = TimeSpan.FromSeconds(1);
	using (Assert.Multiple())
	{
		await Assert.That(record.ResourceId).IsEqualTo(resourceId);
		await Assert.That(record.LockId).IsNotEqualTo(Guid.Empty);
		await Assert.That(record.LockedById).IsEqualTo(Guid.Empty);
		await Assert.That(record.LockedByDescription).IsEqualTo(lockedByDescription);
		await Assert.That(record.TimeToLive).IsEqualTo(timeToLive);
		await Assert.That(record.ValidityTime).IsGreaterThan(timeToLive.Subtract(maxDelay));
		await Assert.That(record.RemainingValidTime).IsGreaterThan(timeToLive.Subtract(maxDelay));
		await Assert.That(record.RemainingValidTime).IsLessThan(timeToLive);
		await Assert.That(record.FetchDate).IsLessThanOrEqualTo(DateTime.Now);
		await Assert.That(record.ExpiresOn).IsLessThanOrEqualTo(DateTime.Now.Add(timeToLive));
		await Assert.That(record.ExpiresOn).IsGreaterThanOrEqualTo(DateTime.Now.Add(timeToLive).Subtract(maxDelay));
		await Assert.That(record.ValidUntil).IsLessThan(DateTime.Now.Add(record.ValidityTime));
		await Assert.That(record.ValidUntil).IsGreaterThan(DateTime.Now.Add(record.ValidityTime).Subtract(maxDelay));
		await Assert.That(record.ValidityTime).IsLessThan(record.TimeToLive);
	}
}

How can I extend assertions to do something like this?:

await Assert.That(record).IsValid(resourceId, timeToLive, lockedByDescription);

[thomhurst]

Create an extension like this:

public static InvokableValueAssertionBuilder<RedisLockRecord> IsValid(this IValueSource<RedisLockRecord> valueSource, string resourceId, TimeSpan timeToLive, string lockedByDescription, [CallerArgumentExpression(nameof(resourceId))] string expression1 = "", [CallerArgumentExpression(nameof(timeToLive))] string expression2 = "", [CallerArgumentExpression(nameof(lockedByDescription))] string expression3 = "")
{
    return valueSource.RegisterAssertion(new RedisLockRecordValidAssertCondition(resourceId, timeToLive, lockedByDescription), [expression1, expression2, expression3]);
}

and create a class representing your assertion with the logic in it.

e.g.:

public class RedisLockRecordValidAssertCondition(string resourceId, TimeSpan timeToLive, string lockedByDescription)
    : BaseAssertCondition<RedisLockRecord>
{
    protected override string GetExpectation()
    {
        return $"is valid with resourceId of {resourceId}, timeToLive of {timeToLive} and lockedByDescription of {lockedByDescription}";
    }

    protected override Task<AssertionResult> GetResult(RedisLockRecord? actualValue, Exception exception)
    {
        return AssertionResult.FailIf(() => actualValue is null, "RedisLockRecord is null")
            .OrFailIf(() => actualValue.ResourceId != resourceId, "Resource id mismatch")
            .OrFailIf(() => actualValue.LockId == Guid.Empty);
            // etc
    }
}

[jesuslpm]

One question. If actualValue is null, will actualValue.ResourceId throw NullReferenceException? or if it is null then the other conditions are not evaluated?

[thomhurst]

It should evaluate and return early on the first failure

[jesuslpm]

So, what I need to do to emulate Assert.Multiple()?

[thomhurst]

You'd have to create that logic yourself. Assert multiple is for combing AssertCondition classes, and you're wrapping everything into one class.