Add floating-point assertions, numeric comparison assertions, Contain for enumerables, and async action assertions

[Copilot]

Adds four missing assertion capabilities needed for projects working with numeric comparisons, enumerable containment, and async code.

New: FloatingPointAssertions<T> (IFloatingPoint<T> constrained)

float and double now get a dedicated assertions type via Should():

result.Reward.Should().BeApproximately(17.5, 0.1);
result.Reward.Should().BeGreaterThanOrEqualTo(0.0);
fileInfo.Length.Should().BeGreaterThan(0L); // also on IntegerAssertions

• BeApproximately(T expected, T precision) — asserts |value − expected| ≤ precision
• BeLessThan, BeLessThanOrEqualTo, BeGreaterThan, BeGreaterThanOrEqualTo
• FloatingPointAssertionsChain<T> for .And chaining

Numeric comparisons on IntegerAssertions<T>

BeLessThan, BeLessThanOrEqualTo, BeGreaterThan, BeGreaterThanOrEqualTo added — leverages the existing IBinaryInteger<T> constraint's IComparisonOperators.

Contain on EnumerableAssertions<TEnumerable, T>

results.Should().Contain(expectedItem);

Asserts the enumerable contains a specific item; throws "Value should contain {expected} but did not." on failure.

New: AsyncActionAssertions for Func<Task>

Async delegates now have a dedicated assertions type via Should(), mirroring the existing ActionAssertions API:

await multiEnvironment.Awaiting(m => m.StopAsync()).Should().ThrowAsync<SomeException>("expected message");
await service.Awaiting(s => s.StartAsync()).Should().NotThrowAsync();

• ThrowAsync<TException>() — asserts the async action throws the specified exception type, returns Task<ActionAssertionsChain<TException>>
• ThrowAsync<TException>(string expectedMessage) — with message check
• NotThrowAsync() — asserts the async action does not throw

InvokingExtensions gains Awaiting<T>(this T value, Func<T, Task> action) and Awaiting<T, TResult>(this T value, Func<T, Task<TResult>> action) for wrapping async methods on a value for assertion testing.

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[MrKWatkins]

You didn't do these points from my list:

4. Async Action Assertions (new type group)

ActionAssertions covers Action only. Required for async delegates (Func):

ThrowAsync<TException>() — asserts the async action throws the specified exception type
ThrowAsync<TException>(string expectedMessage) — with message check
NotThrowAsync() — asserts the async action does not throw

Should mirror the existing ActionAssertions API and chain into ExceptionAssertions.

Entry point needed in ShouldExtensions:

Should(this Func<Task> value) → AsyncActionAssertions

(2 uses, e.g. await multiEnvironment.Awaiting(m => m.StopAsync()).Should().ThrowAsync().WithMessage(...))

Also needed in InvokingExtensions:

Awaiting<T>(this T value, Func<T, Task> action) → Func<Task>

Typed NotThrow<TException>()

ActionAssertions.NotThrow() asserts no exception is thrown. There is also usage of a typed variant that asserts a specific exception type is not thrown (other exceptions may propagate):

NotThrow<TException>() — asserts the action does not throw TException specifically

(e.g. stream.Invoking(s => s.WriteByte(0)).Should().NotThrow())

Change the NotThrow methods, sync and async, for Funcs to return the result of the func afterwards to allow chaining, via a AndResult parameter. E.g. Assert.That(x => x.ToString).Should().NotThrow().And.Result.Should().NotBeNull()

[Copilot]

You didn't do these points from my list:

4. Async Action Assertions (new type group)...

Added in fd1d985:

• AsyncActionAssertions with ThrowAsync<T>(), ThrowAsync<T>(string expectedMessage), and NotThrowAsync() — mirrors the ActionAssertions API and reuses ActionAssertionsChain<TException> for chaining
• Should(this Func<Task>) in ShouldExtensions returning AsyncActionAssertions
• Awaiting<T>(this T, Func<T, Task>) and Awaiting<T, TResult>(this T, Func<T, Task<TResult>>) in InvokingExtensions

Usage example:

await multiEnvironment.Awaiting(m => m.StopAsync()).Should().ThrowAsync<SomeException>("expected message");