CODEWITHSUNDEEP
unit-testingmstestxunit
sduplooy
sduplooy

Reputation: 14720

Unit test exception messages with xUnit

I'm currently converting my MsTest unit tests to xUnit. With xUnit, is there a way to test exception messages? Is it correct to test exception messages as opposed just the exception type?

Upvotes: 83

Views: 33521

Answers (8)

Ashitha
Ashitha

Reputation: 1

Better to use the Record.Exception method:

[Fact]
public void Update_Record_ExpectException()
{
    var sut = new RecordData();
    var exception = Record.Exception(() => sut.Update(10));
    Assert.IsType(typeof(ArgumentNullException), exception);
}

Hope this helps ...

Upvotes: 0

user1829319
user1829319

Reputation: 743

Better to use the Record.Exception method as it matches the AAA pattern:

[Fact]
public void Divide_TwoNumbers_ExpectException()
{
    var sut = new Calculator();
    var exception = Record.Exception(() => sut.Divide(10, 0));
    Assert.IsType(typeof(DivideByZeroException), exception);
}

Hope this helps ...

Upvotes: 11

the_joric
the_joric

Reputation: 12226

I think it is correct to test for both Exception type and message. And both are easy in xUnit:

var exception = Assert.Throws<AuthenticationException>(() => DoSomething());
Assert.Equal(message, exception.Message);

Upvotes: 148

user2982369
user2982369

Reputation: 21

Something like this:

var ex = Record.Exception(() => DoSomeThing());
Assert.IsType(typeof(ArgumentNullException), ex);
Assert.Contains("Your exception message", ex.Message);

Upvotes: 2

Nico Degraef
Nico Degraef

Reputation: 155

In the light of async stuff, new version would be

var ex = await Record.ExceptionAsync(() => myMethod(myParams));
Assert.IsType<SomeException>(ex);
Assert.Equal("My text of the error.", ex.Message);

Upvotes: 0

Andy Creigh
Andy Creigh

Reputation: 113

BTW, Resharper prefers not to use typeof and suggests Assert.IsType instead, e.g.

var ex = Record.Exception(() => new FooController(null, null));
Assert.IsType<ArgumentNullException>(ex);

Upvotes: 1

NerdFury
NerdFury

Reputation: 19214

xUnit uses Assert.Throws to test for exception types. You could catch the exception and Assert against the message if you needed. I think in general you want to test that the expected exception is thrown, and the exact message is really not necessary.

Assert.Throws<ArgumentNullException>()

The exception might be if you have a custom exception you are unit testing and you want to make sure the message generated is what you expect. Or if there are two ways that the same exception type can be thrown but with different messages, then asserting against the message would be valuable

Upvotes: 0

RonK
RonK

Reputation: 9652

An exception is no different than any other expected result of your test. It is natural to test that the message is the correct one as two different messages can come in the same exception type. However - I personally don't think of it as mandatory, at least not in all exceptions.

In our project each application exception also has a 'Message' object attached to it, so we verify the MessageId only, we don't verify that the message arguments are correct or the message's text. E.g if the message text is "Wrong parameter <{0}> was provided", we don't check that the argument that was passed to format {0} is as expected - this is not the intent. The message has a unique id - so we verify that the MessageID on the exception is 'WRONG_PARAMETER_PROVIDED'.

Upvotes: 0

Related Questions