Add .ThrowsAsync() that will correctly mock exception on async meth…

…ods. (nsubstitute#609)
Socolin · Aug 29, 2021 · f84efda · f84efda
1 parent 680df07
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diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -1,5 +1,6 @@
 ### unreleased
 * [NEW] Add .NET 5 support
+* [NEW] Add `.ThrowsAsync()` that will correctly mock exception on async methods. (#609)
 
 ### 4.2.2 (Jun 2020)
 

diff --git a/src/NSubstitute/Extensions/ExceptionExtensions.cs b/src/NSubstitute/Extensions/ExceptionExtensions.cs
@@ -1,4 +1,9 @@
 using System;
+using System.Linq;
+using System.Reflection;
+#if !NET45
+using System.Threading.Tasks;
+#endif
 using NSubstitute.Core;
 
 // Disable nullability for client API, so it does not affect clients.
@@ -67,5 +72,181 @@ public static ConfiguredCall ThrowsForAnyArgs<TException>(this object value)
         /// <returns></returns>
         public static ConfiguredCall ThrowsForAnyArgs(this object value, Func<CallInfo, Exception> createException) =>
             value.ReturnsForAnyArgs(ci => throw createException(ci));
+
+#if !NET45
+        /// <summary>
+        /// Throw an exception for this call.
+        /// </summary>
+        /// <param name="value"></param>
+        /// <param name="ex">Exception to throw</param>
+        /// <returns></returns>
+        public static ConfiguredCall ThrowsAsync(this Task value, Exception ex) =>
+            value.Returns(_ => Task.FromException(ex));
+
+        /// <summary>
+        /// Throw an exception for this call.
+        /// </summary>
+        /// <param name="value"></param>
+        /// <param name="ex">Exception to throw</param>
+        /// <returns></returns>
+        public static ConfiguredCall ThrowsAsync<T>(this Task<T> value, Exception ex) =>
+            value.Returns(_ => Task.FromException<T>(ex));
+
+        /// <summary>
+        /// Throw an exception of the given type for this call.
+        /// </summary>
+        /// <typeparam name="TException">Type of exception to throw</typeparam>
+        /// <param name="value"></param>
+        /// <returns></returns>
+        public static ConfiguredCall ThrowsAsync<TException>(this Task value)
+            where TException : notnull, Exception, new()
+        {
+            return value.Returns(_ => FromException(value, new TException()));
+        }
+
+        /// <summary>
+        /// Throw an exception for this call, as generated by the specified function.
+        /// </summary>
+        /// <param name="value"></param>
+        /// <param name="createException">Func creating exception object</param>
+        /// <returns></returns>
+        public static ConfiguredCall ThrowsAsync(this Task value, Func<CallInfo, Exception> createException) =>
+            value.Returns(ci => Task.FromException(createException(ci)));
+
+        /// <summary>
+        /// Throw an exception for this call, as generated by the specified function.
+        /// </summary>
+        /// <param name="value"></param>
+        /// <param name="createException">Func creating exception object</param>
+        /// <returns></returns>
+        public static ConfiguredCall ThrowsAsync<T>(this Task<T> value, Func<CallInfo, Exception> createException) =>
+            value.Returns(ci => Task.FromException<T>(createException(ci)));
+
+        /// <summary>
+        /// Throw an exception for this call made with any arguments.
+        /// </summary>
+        /// <param name="value"></param>
+        /// <param name="ex">Exception to throw</param>
+        /// <returns></returns>
+        public static ConfiguredCall ThrowsAsyncForAnyArgs(this Task value, Exception ex) =>
+            value.ReturnsForAnyArgs(_ => Task.FromException(ex));
+
+        /// <summary>
+        /// Throw an exception for this call made with any arguments.
+        /// </summary>
+        /// <param name="value"></param>
+        /// <param name="ex">Exception to throw</param>
+        /// <returns></returns>
+        public static ConfiguredCall ThrowsAsyncForAnyArgs<T>(this Task<T> value, Exception ex) =>
+            value.ReturnsForAnyArgs(_ => Task.FromException<T>(ex));
+
+        /// <summary>
+        /// Throws an exception of the given type for this call made with any arguments.
+        /// </summary>
+        /// <typeparam name="TException">Type of exception to throw</typeparam>
+        /// <param name="value"></param>
+        /// <returns></returns>
+        public static ConfiguredCall ThrowsAsyncForAnyArgs<TException>(this Task value)
+            where TException : notnull, Exception, new()
+        {
+            return value.ReturnsForAnyArgs(_ => FromException(value, new TException()));
+        }
+
+        /// <summary>
+        /// Throws an exception for this call made with any arguments, as generated by the specified function.
+        /// </summary>
+        /// <param name="value"></param>
+        /// <param name="createException">Func creating exception object</param>
+        /// <returns></returns>
+        public static ConfiguredCall ThrowsAsyncForAnyArgs(this Task value, Func<CallInfo, Exception> createException) =>
+            value.ReturnsForAnyArgs(ci => Task.FromException(createException(ci)));
+
+        /// <summary>
+        /// Throws an exception for this call made with any arguments, as generated by the specified function.
+        /// </summary>
+        /// <param name="value"></param>
+        /// <param name="createException">Func creating exception object</param>
+        /// <returns></returns>
+        public static ConfiguredCall ThrowsAsyncForAnyArgs<T>(this Task<T> value, Func<CallInfo, Exception> createException) =>
+            value.ReturnsForAnyArgs(ci => Task.FromException<T>(createException(ci)));
+
+#if NETSTANDARD2_1_OR_GREATER || NETCOREAPP2_1_OR_GREATER
+        /// <summary>
+        /// Throw an exception for this call.
+        /// </summary>
+        /// <param name="value"></param>
+        /// <param name="ex">Exception to throw</param>
+        /// <returns></returns>
+        public static ConfiguredCall ThrowsAsync<T>(this ValueTask<T> value, Exception ex) =>
+            value.Returns(_ => ValueTask.FromException<T>(ex));
+
+        /// <summary>
+        /// Throw an exception of the given type for this call.
+        /// </summary>
+        /// <typeparam name="TResult">Type of exception to throw</typeparam>
+        /// <typeparam name="TException">Type of exception to throw</typeparam>
+        /// <param name="value"></param>
+        /// <returns></returns>
+        public static ConfiguredCall ThrowsAsync<TResult, TException>(this ValueTask<TResult> value)
+            where TException : notnull, Exception, new()
+        {
+            return value.Returns(_ => ValueTask.FromException<TResult>(new TException()));
+        }
+
+        /// <summary>
+        /// Throw an exception for this call, as generated by the specified function.
+        /// </summary>
+        /// <param name="value"></param>
+        /// <param name="createException">Func creating exception object</param>
+        /// <returns></returns>
+        public static ConfiguredCall ThrowsAsync<T>(this ValueTask<T> value, Func<CallInfo, Exception> createException) =>
+            value.Returns(ci => ValueTask.FromException<T>(createException(ci)));
+
+        /// <summary>
+        /// Throws an exception of the given type for this call made with any arguments.
+        /// </summary>
+        /// <typeparam name="T"></typeparam>
+        /// <typeparam name="TException">Type of exception to throw</typeparam>
+        /// <param name="value"></param>
+        /// <returns></returns>
+        public static ConfiguredCall ThrowsAsyncForAnyArgs<T, TException>(this ValueTask<T> value)
+            where TException : notnull, Exception, new()
+        {
+            return value.ReturnsForAnyArgs(_ => ValueTask.FromException<T>(new TException()));
+        }
+
+        /// <summary>
+        /// Throw an exception for this call made with any arguments.
+        /// </summary>
+        /// <param name="value"></param>
+        /// <param name="ex">Exception to throw</param>
+        /// <returns></returns>
+        public static ConfiguredCall ThrowsAsyncForAnyArgs<T>(this ValueTask<T> value, Exception ex) =>
+            value.ReturnsForAnyArgs(_ => ValueTask.FromException<T>(ex));
+
+        /// <summary>
+        /// Throws an exception for this call made with any arguments, as generated by the specified function.
+        /// </summary>
+        /// <param name="value"></param>
+        /// <param name="createException">Func creating exception object</param>
+        /// <returns></returns>
+        public static ConfiguredCall ThrowsAsyncForAnyArgs<T>(this ValueTask<T> value, Func<CallInfo, Exception> createException) =>
+            value.ReturnsForAnyArgs(ci => ValueTask.FromException<T>(createException(ci)));
+#endif
+
+        private static object FromException(object value, Exception exception)
+        {
+            // Handle Task<T>
+            var valueType = value.GetType();
+            if (valueType.IsConstructedGenericType)
+            {
+                var fromExceptionMethodInfo = typeof(Task).GetMethods(BindingFlags.Static | BindingFlags.Public).Single(m => m.Name == "FromException" && m.ContainsGenericParameters);
+                var specificFromExceptionMethod = fromExceptionMethodInfo.MakeGenericMethod(valueType.GenericTypeArguments);
+                return specificFromExceptionMethod.Invoke(null, new object[] {exception});
+            }
+
+            return Task.FromException(exception);
+        }
+#endif
     }
 }
diff --git a/tests/NSubstitute.Acceptance.Specs/Infrastructure/ISomething.cs b/tests/NSubstitute.Acceptance.Specs/Infrastructure/ISomething.cs
@@ -19,14 +19,17 @@ public interface ISomething
 
         object this[string key] { get; set; }
         System.Threading.Tasks.Task Async();
+        System.Threading.Tasks.Task DoAsync(object stuff);
         System.Threading.Tasks.Task<int> CountAsync();
+        System.Threading.Tasks.Task<int> AnythingAsync(object stuff);
         System.Threading.Tasks.Task<string> EchoAsync(int i);
         System.Threading.Tasks.Task<string> SayAsync(string s);
         System.Threading.Tasks.Task<SomeClass> SomeActionAsync();
         System.Threading.Tasks.Task<SomeClass> SomeActionWithParamsAsync(int i, string s);
 
         System.Threading.Tasks.ValueTask<int> CountValueTaskAsync();
         System.Threading.Tasks.ValueTask<string> EchoValueTaskAsync(int i);
+        System.Threading.Tasks.ValueTask<int> AnythingValueTaskAsync(object stuff);
         System.Threading.Tasks.ValueTask<string> SayValueTaskAsync(string s);
         System.Threading.Tasks.ValueTask<SomeClass> SomeActionValueTaskAsync();
         System.Threading.Tasks.ValueTask<SomeClass> SomeActionWithParamsValueTaskAsync(int i, string s);