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c#.netnunitexception
Jason More
Jason More

Reputation: 7073

nUnit Assert.That(method,Throws.Exception) not catching exceptions

Can someone tell me why this unit test that checks for exceptions fails? Obviously my real test is checking other code but I'm using Int32.Parse to show the issue.

[Test]
public void MyTest()
{
    Assert.That(Int32.Parse("abc"), Throws.Exception.TypeOf<FormatException>());
}

The test fails, giving this error. Obviously I'm trying to test for this exception and I think I'm missing something in my syntax.

Error   1   TestCase '.MyTest'
failed: System.FormatException : Input string was not in a correct format.
at System.Number.StringToNumber(String str, NumberStyles options, NumberBuffer& number, NumberFormatInfo info, Boolean parseDecimal)
at System.Number.ParseInt32(String s, NumberStyles style, NumberFormatInfo info)
at System.Int32.Parse(String s)

based on the documentation at Throws Constraint (NUnit 2.5)

Upvotes: 50

Views: 23239

Answers (2)

Klaus Byskov Pedersen
Klaus Byskov Pedersen

Reputation: 120927

Try this instead: 

Assert.That(() => Int32.Parse("abc"), Throws.Exception.TypeOf<FormatException>());

Basically you need to pass a delegate to Assert.That, just like the documentation in your link states (note that I've used a lambda expression here, but it should be the same).

Upvotes: 80

ermau
ermau

Reputation: 1303

What test runner are you using? Not all of them work correctly with the exception assertions.

You may have better luck using [ExpectedException (typeof(FormatException))] or even Assert.Throws<FormatException> (() => Int32.Parse("abc"));

Upvotes: 9

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