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SeanKilleen merged 1 commit into from
Oct 22, 2026
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Document that Assert.That now evaluates Func<T> actual values in NUnit 5 #1270

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25 changes: 25 additions & 0 deletions docs/articles/nunit/V5BreakingChanges.md
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Expand Up @@ -38,6 +38,31 @@ Issues [#5253](https://github.com/nunit/nunit/issues/5253) and [#5265](https://g
> `global`, at the top of each file that needs them. This doesn't work for `ActualValueDelegate<T>`, because C# aliases
> can't be open generic types. Replace that one with `Func<T>`.

The new overloads also change what happens when the *actual* value is itself a delegate:

> [!WARNING]
> Because `Assert.That` now has a `Func<T>` overload, a `Func<T>` passed as the *actual* value is **evaluated**, and the
> constraint is applied to its result. In NUnit 4.5 and earlier, a `Func<T>` only matched the generic `TActual`
> overload, so the constraint was applied to the delegate itself. For example:
>
> ```csharp
> Func<bool> testFunc = CreateFunc();
>
> // NUnit 4.5: checks that the delegate is not null.
> // NUnit 5.0: calls testFunc() and checks that the returned bool is not null, which always passes.
> Assert.That(testFunc, Is.Not.Null);
> ```
>
> To assert on the delegate rather than on its result, cast it to `object` or use the classic assertion:
>
> ```csharp
> Assert.That((object)testFunc, Is.Not.Null);
> ClassicAssert.IsNotNull(testFunc);
> ```
>
> The [NUnit.Analyzers](xref:nunitanalyzers) package reports an error when a constraint such as `Is.Not.Null` is
> applied to a value type like `bool`, which makes this change easier to spot.

### `Assert.ThrowsAsync`, `Assert.CatchAsync` and `Assert.DoesNotThrowAsync` must be awaited

Issue [#4384](https://github.com/nunit/nunit/issues/4384)
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