MustHaveLength for ImmutableArray

Context

The .NET library Light.GuardClauses already has several assertions for collections. They often rely on IEnumerable<T> or IEnumerable. However, these assertions would result in ImmutableArray<T> being boxed - we want to avoid that by providing dedicated assertions for this type which avoids boxing. For this issue, we implement the MustHaveLength assertion for ImmutableArray<T>.

Tasks for this issue

• The production code should be placed in the Light.GuardClauses project. The file Check.MustHaveLength.cs already exists in the root folder of the project - extend this existing file.
• In this file, create several extension method overloads called MustHaveLength for ImmutableArray<T>. It should be placed in the class Check which is marked as partial.
• Each assertion in Light.GuardClauses has two overloads - the first one takes the optional parameterName and message arguments and throw the default exception. The actual exception is thrown in the Throw class - use the existing Throw.InvalidCollectionCount method which is located in ExceptionFactory/Throw.InvalidCollectionCount.cs.
• The other overload takes a delegate which allows the caller to provide their own custom exceptions. Use the existing Throw.CustomException method and pass the delegate, the erroneous ImmutableArray<T> instance and the expected length.
• Use the Length property of ImmutableArray<T> instead of Count for performance and correctness.
• Create unit tests for both overloads. The corresponding tests should be placed in Light.GuardClauses.Tests project. There is already a file 'StringAssertions/MustHaveLengthTests.cs' but you need to create a new file 'CollectionAssertions/MustHaveLengthTests.cs' for collection-related length tests. Please follow conventions of the existing tests (e.g. use FluentAssertions' Should() for assertions).

Notes

• There are already plenty of other assertions and tests in this library. All overloads are placed in the same file in the production code project. The test projects has top-level folders for different groups of assertions, like CollectionAssertions, StringAssertions, DateTimeAssertions and so on. Please take a look at them to follow a similar structure and code style.
• This assertion specifically targets ImmutableArray<T> to avoid boxing that would occur with generic IEnumerable<T> extensions.
• Use the Length property instead of Count as this is the appropriate property for ImmutableArray<T>.
• The assertion should verify that the ImmutableArray<T> has exactly the expected length.
• If you have any questions or suggestions, please ask me about them.