Allow WithoutMessage when using Should().Throw() and ThrowAsync() by dennisdoomen · Pull Request #3100 · fluentassertions/fluentassertions · GitHub
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Allow WithoutMessage when using Should().Throw() and ThrowAsync() #3100

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Merged
dennisdoomen merged 1 commit into from
Sep 23, 2025
Merged

Allow WithoutMessage when using Should().Throw() and ThrowAsync() #3100

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9 changes: 9 additions & 0 deletions Src/FluentAssertions/Equivalency/Steps/AssertionResultSet.cs
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24 changes: 24 additions & 0 deletions Src/FluentAssertions/ExceptionAssertionsExtensions.cs
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Expand Up @@ -35,6 +35,30 @@ public static async Task<ExceptionAssertions<TException>> WithMessage<TException
return (await task).WithMessage(expectedWildcardPattern, because, becauseArgs);
}

/// <summary>
/// Asserts that the thrown exception does NOT have a message that matches <paramref name="wildcardPattern" />.
/// </summary>
/// <param name="task">The <see cref="ExceptionAssertions{TException}"/> containing the thrown exception.</param>
/// <param name="wildcardPattern">
/// The wildcard pattern with which the exception message is matched, where * and ? have special meanings.
/// </param>
/// <param name="because">
/// A formatted phrase as is supported by <see cref="string.Format(string,object[])" /> explaining why the assertion
/// is needed. If the phrase does not start with the word <i>because</i>, it is prepended automatically.
/// </param>
/// <param name="becauseArgs">
/// Zero or more objects to format using the placeholders in <paramref name="because"/>.
/// </param>
public static async Task<ExceptionAssertions<TException>> WithoutMessage<TException>(
this Task<ExceptionAssertions<TException>> task,
string wildcardPattern,
[StringSyntax("CompositeFormat")] string because = "",
params object[] becauseArgs)
where TException : Exception
{
return (await task).WithoutMessage(wildcardPattern, because, becauseArgs);
}

/// <summary>
/// Asserts that the exception matches a particular condition.
/// </summary>
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58 changes: 54 additions & 4 deletions Src/FluentAssertions/Specialized/ExceptionAssertions.cs
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Expand Up @@ -84,24 +84,74 @@ public virtual ExceptionAssertions<TException> WithMessage(string expectedWildca
.ForCondition(Subject.Any())
.FailWith("Expected exception with message {0}{reason}, but no exception was thrown.", expectedWildcardPattern);

AssertExceptionMessage(expectedWildcardPattern, because, becauseArgs);
AssertExceptionMessage(message =>
message.Should().MatchEquivalentOf(expectedWildcardPattern, because, becauseArgs));

return this;
}

private void AssertExceptionMessage(string expectedWildcardPattern, string because, object[] becauseArgs)
/// <summary>
/// Asserts that the thrown exception does NOT have a message that matches <paramref name="wildcardPattern" />.
/// </summary>
/// <param name="wildcardPattern">
/// The pattern to match against the exception message. This parameter can contain a combination of literal text and
/// wildcard (* and ?) characters, but it doesn't support regular expressions.
/// </param>
/// <param name="because">
/// A formatted phrase as is supported by <see cref="string.Format(string,object[])" /> explaining why the assertion
/// is needed. If the phrase does not start with the word <i>because</i>, it is prepended automatically.
/// </param>
/// <param name="becauseArgs">
/// Zero or more objects to format using the placeholders in <paramref name="because"/>.
/// </param>
/// <remarks>
/// <paramref name="wildcardPattern"/> can be a combination of literal and wildcard characters,
/// but it doesn't support regular expressions. The following wildcard specifiers are permitted in
/// <paramref name="wildcardPattern"/>.
/// <list type="table">
/// <listheader>
/// <term>Wildcard character</term>
/// <description>Description</description>
/// </listheader>
/// <item>
/// <term>* (asterisk)</term>
/// <description>Zero or more characters in that position.</description>
/// </item>
/// <item>
/// <term>? (question mark)</term>
/// <description>Exactly one character in that position.</description>
/// </item>
/// </list>
/// </remarks>
public virtual ExceptionAssertions<TException> WithoutMessage(string wildcardPattern,
[StringSyntax("CompositeFormat")] string because = "", params object[] becauseArgs)
{
assertionChain
.BecauseOf(because, becauseArgs)
.UsingLineBreaks
.ForCondition(Subject.Any())
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.FailWith("Expected exception without message matching {0}{reason}, but no exception was thrown.", wildcardPattern);

AssertExceptionMessage(message =>
message.Should().NotMatchEquivalentOf(wildcardPattern, because, becauseArgs));
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return this;
}

private void AssertExceptionMessage(Action<string> messageAssertion)
{
var results = new AssertionResultSet();

foreach (string message in Subject.Select(exc => exc.Message))
{
using (var scope = new AssertionScope())
{
// Treat every assertion within the scope as a new independent one.
var chain = AssertionChain.GetOrCreate();
chain.OverrideCallerIdentifier(() => "exception message");
chain.OverrideCallerIdentifier(() => "the exception message");
chain.ReuseOnce();

message.Should().MatchEquivalentOf(expectedWildcardPattern, because, becauseArgs);
messageAssertion(message);

results.AddSet(message, scope.Discard());
}
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3 changes: 3 additions & 0 deletions Tests/Approval.Tests/ApprovedApi/FluentAssertions/net47.verified.txt
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Expand Up @@ -245,6 +245,8 @@ namespace FluentAssertions
where TException : System.ArgumentException { }
public static System.Threading.Tasks.Task<FluentAssertions.Specialized.ExceptionAssertions<TException>> WithParameterName<TException>(this System.Threading.Tasks.Task<FluentAssertions.Specialized.ExceptionAssertions<TException>> task, string paramName, string because = "", params object[] becauseArgs)
where TException : System.ArgumentException { }
public static System.Threading.Tasks.Task<FluentAssertions.Specialized.ExceptionAssertions<TException>> WithoutMessage<TException>(this System.Threading.Tasks.Task<FluentAssertions.Specialized.ExceptionAssertions<TException>> task, string wildcardPattern, string because = "", params object[] becauseArgs)
where TException : System.Exception { }
}
public static class FluentActions
{
Expand Down Expand Up @@ -2166,6 +2168,7 @@ namespace FluentAssertions.Specialized
public virtual FluentAssertions.Specialized.ExceptionAssertions<TInnerException> WithInnerExceptionExactly<TInnerException>(string because = "", params object[] becauseArgs)
where TInnerException : System.Exception { }
public virtual FluentAssertions.Specialized.ExceptionAssertions<TException> WithMessage(string expectedWildcardPattern, string because = "", params object[] becauseArgs) { }
public virtual FluentAssertions.Specialized.ExceptionAssertions<TException> WithoutMessage(string wildcardPattern, string because = "", params object[] becauseArgs) { }
}
public class ExecutionTime
{
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3 changes: 3 additions & 0 deletions Tests/Approval.Tests/ApprovedApi/FluentAssertions/net6.0.verified.txt
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Expand Up @@ -260,6 +260,8 @@ namespace FluentAssertions
where TException : System.ArgumentException { }
public static System.Threading.Tasks.Task<FluentAssertions.Specialized.ExceptionAssertions<TException>> WithParameterName<TException>(this System.Threading.Tasks.Task<FluentAssertions.Specialized.ExceptionAssertions<TException>> task, string paramName, string because = "", params object[] becauseArgs)
where TException : System.ArgumentException { }
public static System.Threading.Tasks.Task<FluentAssertions.Specialized.ExceptionAssertions<TException>> WithoutMessage<TException>(this System.Threading.Tasks.Task<FluentAssertions.Specialized.ExceptionAssertions<TException>> task, string wildcardPattern, string because = "", params object[] becauseArgs)
where TException : System.Exception { }
}
public static class FluentActions
{
Expand Down Expand Up @@ -2301,6 +2303,7 @@ namespace FluentAssertions.Specialized
public virtual FluentAssertions.Specialized.ExceptionAssertions<TInnerException> WithInnerExceptionExactly<TInnerException>(string because = "", params object[] becauseArgs)
where TInnerException : System.Exception { }
public virtual FluentAssertions.Specialized.ExceptionAssertions<TException> WithMessage(string expectedWildcardPattern, string because = "", params object[] becauseArgs) { }
public virtual FluentAssertions.Specialized.ExceptionAssertions<TException> WithoutMessage(string wildcardPattern, string because = "", params object[] becauseArgs) { }
}
public class ExecutionTime
{
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3 changes: 3 additions & 0 deletions Tests/Approval.Tests/ApprovedApi/FluentAssertions/netstandard2.0.verified.txt
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Expand Up @@ -237,6 +237,8 @@ namespace FluentAssertions
where TException : System.ArgumentException { }
public static System.Threading.Tasks.Task<FluentAssertions.Specialized.ExceptionAssertions<TException>> WithParameterName<TException>(this System.Threading.Tasks.Task<FluentAssertions.Specialized.ExceptionAssertions<TException>> task, string paramName, string because = "", params object[] becauseArgs)
where TException : System.ArgumentException { }
public static System.Threading.Tasks.Task<FluentAssertions.Specialized.ExceptionAssertions<TException>> WithoutMessage<TException>(this System.Threading.Tasks.Task<FluentAssertions.Specialized.ExceptionAssertions<TException>> task, string wildcardPattern, string because = "", params object[] becauseArgs)
where TException : System.Exception { }
}
public static class FluentActions
{
Expand Down Expand Up @@ -2110,6 +2112,7 @@ namespace FluentAssertions.Specialized
public virtual FluentAssertions.Specialized.ExceptionAssertions<TInnerException> WithInnerExceptionExactly<TInnerException>(string because = "", params object[] becauseArgs)
where TInnerException : System.Exception { }
public virtual FluentAssertions.Specialized.ExceptionAssertions<TException> WithMessage(string expectedWildcardPattern, string because = "", params object[] becauseArgs) { }
public virtual FluentAssertions.Specialized.ExceptionAssertions<TException> WithoutMessage(string wildcardPattern, string because = "", params object[] becauseArgs) { }
}
public class ExecutionTime
{
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3 changes: 3 additions & 0 deletions Tests/Approval.Tests/ApprovedApi/FluentAssertions/netstandard2.1.verified.txt
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Expand Up @@ -245,6 +245,8 @@ namespace FluentAssertions
where TException : System.ArgumentException { }
public static System.Threading.Tasks.Task<FluentAssertions.Specialized.ExceptionAssertions<TException>> WithParameterName<TException>(this System.Threading.Tasks.Task<FluentAssertions.Specialized.ExceptionAssertions<TException>> task, string paramName, string because = "", params object[] becauseArgs)
where TException : System.ArgumentException { }
public static System.Threading.Tasks.Task<FluentAssertions.Specialized.ExceptionAssertions<TException>> WithoutMessage<TException>(this System.Threading.Tasks.Task<FluentAssertions.Specialized.ExceptionAssertions<TException>> task, string wildcardPattern, string because = "", params object[] becauseArgs)
where TException : System.Exception { }
}
public static class FluentActions
{
Expand Down Expand Up @@ -2166,6 +2168,7 @@ namespace FluentAssertions.Specialized
public virtual FluentAssertions.Specialized.ExceptionAssertions<TInnerException> WithInnerExceptionExactly<TInnerException>(string because = "", params object[] becauseArgs)
where TInnerException : System.Exception { }
public virtual FluentAssertions.Specialized.ExceptionAssertions<TException> WithMessage(string expectedWildcardPattern, string because = "", params object[] becauseArgs) { }
public virtual FluentAssertions.Specialized.ExceptionAssertions<TException> WithoutMessage(string wildcardPattern, string because = "", params object[] becauseArgs) { }
}
public class ExecutionTime
{
Expand Down
2 changes: 1 addition & 1 deletion ...ecs/Exceptions/ExceptionAssertionSpecs.cs → ...ecs/Exceptions/AggregateExceptionSpecs.cs
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Expand Up @@ -4,7 +4,7 @@

namespace FluentAssertions.Specs.Exceptions;

public class ExceptionAssertionSpecs
public class AggregateExceptionSpecs
{
[Fact]
public void When_method_throws_an_empty_AggregateException_it_should_fail()
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65 changes: 65 additions & 0 deletions Tests/FluentAssertions.Specs/Exceptions/ExceptionMessageSpecs.cs
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@@ -0,0 +1,65 @@
using System;
using System.Threading.Tasks;
using FluentAssertions.Execution;
using Xunit;
using Xunit.Sdk;

namespace FluentAssertions.Specs.Exceptions;

public class ExceptionMessageSpecs
{
[Fact]
public void Can_assert_the_exception_message_does_not_include_a_specific_string()
{
// Arrange
Action throwException = () => throw new InvalidOperationException("Something bad happened");

// Act
Action act = () => throwException.Should()
.Throw<InvalidOperationException>()
.WithoutMessage("*bad*")
.Which.Should().Be(typeof(InvalidOperationException));

// Assert
act.Should().Throw<XunitException>()
.WithMessage(
"Did not expect the exception message to match the equivalent of \"*bad*\", but \"Something bad happened\" matches.");
}

[Fact]
public void Only_check_the_message_of_an_actual_exception()
{
// Arrange
Action dontThrowAtAll = () => { };

// Act
var act = () =>
{
using var _ = new AssertionScope();

return dontThrowAtAll.Should()
.Throw<InvalidOperationException>()
.WithoutMessage("*bad*");
};

// Assert
act.Should().Throw<XunitException>()
.WithMessage(
"Expected*System.InvalidOperationException*no exception*");
}

[Fact]
public async Task Can_assert_an_async_exception_message_does_not_include_a_specific_string()
{
// Arrange
Func<Task> throwsAsync = () => throw new AggregateException(new ArgumentException("That was wrong."));

// Act
var act = () => throwsAsync.Should().ThrowAsync<ArgumentException>().WithoutMessage("That was wrong.");

// Assert
await act.Should().ThrowAsync<XunitException>()
.WithMessage(
"Did not expect the exception message to match the equivalent of \"*wrong*\", but \"That was wrong.\" matches.");
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}
}
20 changes: 10 additions & 10 deletions Tests/FluentAssertions.Specs/Exceptions/OuterExceptionSpecs.cs
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Expand Up @@ -37,7 +37,7 @@ public void When_subject_throws_expected_exception_but_with_unexpected_message_i
{
// Assert
ex.Message.Should().Match(
"Expected exception message to match the equivalent of*\"some message\", but*\"some\" does not*");
"Expected the exception message to match the equivalent of*\"some message\", but*\"some\" does not*");
}
}

Expand All @@ -62,7 +62,7 @@ public void Long_exception_messages_are_rendered_over_multiple_lines()
// Assert
ex.Message.Should().Match(
"""
Expected exception message to match the equivalent of
Expected the exception message to match the equivalent of

"*",

Expand Down Expand Up @@ -100,7 +100,7 @@ public void Multiline_exception_messages_are_rendered_over_multiple_lines()
// Assert
ex.Message.Should().Match(
"""
Expected exception message to match the equivalent of
Expected the exception message to match the equivalent of

"line1*
line2",
Expand Down Expand Up @@ -135,7 +135,7 @@ public void Short_exception_messages_are_rendered_on_a_single_line()
{
// Assert
ex.Message.Should().Match(
"""Expected exception message to match the equivalent of "*", but "some" does not.""");
"""Expected the exception message to match the equivalent of "*", but "some" does not.""");
}
}

Expand Down Expand Up @@ -168,7 +168,7 @@ public void When_subject_throws_expected_exception_with_message_that_does_not_st
// Assert
action.Should().Throw<Exception>()
.WithMessage(
"Expected exception message to match the equivalent of*\"Expected mes*\", but*\"OxpectOd message\" does not*");
"Expected the exception message to match the equivalent of*\"Expected mes*\", but*\"OxpectOd message\" does not*");
}

[Fact]
Expand Down Expand Up @@ -201,7 +201,7 @@ public void When_subject_throws_expected_exception_with_message_that_does_not_st
// Assert
action.Should().Throw<Exception>()
.WithMessage(
"Expected exception message to match the equivalent of*\"expected mes*\", but*\"OxpectOd message\" does not*");
"Expected the exception message to match the equivalent of*\"expected mes*\", but*\"OxpectOd message\" does not*");
}

[Fact]
Expand All @@ -224,7 +224,7 @@ public void When_subject_throws_some_exception_with_unexpected_message_it_should
{
// Assert
ex.Message.Should().Match(
"Expected exception message to match the equivalent of \"message2\" because we want to test the failure message, but \"message1\" does not*");
"Expected the exception message to match the equivalent of \"message2\" because we want to test the failure message, but \"message1\" does not*");
}
}

Expand All @@ -248,7 +248,7 @@ public void When_subject_throws_some_exception_with_an_empty_message_it_should_t
{
// Assert
ex.Message.Should().Match(
"Expected exception message to match the equivalent of \"message2\"*, but \"\"*");
"Expected the exception message to match the equivalent of \"message2\"*, but \"\"*");
}
}

Expand All @@ -272,7 +272,7 @@ public void
{
// Assert
ex.Message.Should().Match(
"Expected exception message to match the equivalent of*\"message2\",*but*message2*someParam*");
"Expected the exception message to match the equivalent of*\"message2\",*but*message2*someParam*");
}
}

Expand Down Expand Up @@ -343,7 +343,7 @@ public void When_subject_throws_exception_with_message_with_braces_but_a_differe
{
// Assert
ex.Message.Should().Match(
"Expected exception message to match the equivalent of*\"message without\"*, but*\"message with {}*");
"Expected the exception message to match the equivalent of*\"message without\"*, but*\"message with {}*");
}
}

Expand Down
1 change: 1 addition & 0 deletions docs/_pages/releases.md
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