Passing single value to params argument in NUnit TestCase

Question

I have the following test:

[ExpectedException(typeof(ParametersParseException))]
[TestCase("param1")]
[TestCase("param1", "param2")]
[TestCase("param1", "param2", "param3", "optParam4", "optParam5", "some extra parameter")]
public void Parse_InvalidParametersNumber_ThrowsException(params string[] args)
{
    new ParametersParser(args).Parse();
}

The first TestCase (obviously) fails with the following error:

System.ArgumentException : Object of type 'System.String' 
cannot be converted to type 'System.String[]'.

I tried to replace the TestCase definition with this one:

[TestCase(new[] { param1 })]

but now I get the following compilation error:

error CS0182: An attribute argument must be a constant expression, typeof expression or array creation expression of an attribute parameter type

My solution for now is moving the 'one parameter' case to a different test method.

Still, is there a way to get this test to run the same way as the others?

score 9 · Accepted Answer · answered Mar 03 '12 at 21:40

9

One way could be to use TestCaseSource, and have a method that returns each parameter set, instead of using TestCase.

answered Mar 03 '12 at 21:40

AdaTheDev

142,592
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score 3 · Answer 2 · edited May 23 '17 at 10:28

3

Based on this answer in response to the question 'NUnit cannot recognize a TestCase when it contains an array', the compilation error stems from a bug, and can be overcome using the syntax for named test cases, as such:

[ExpectedException(typeof(ParametersParseException))]
[TestCase(new[] { "param1"}, TestName="SingleParam")]
[TestCase(new[] { "param1", "param2"}, TestName="TwoParams")]
[TestCase(new[] { "param1", "param2", "param3", "optParam4", "optParam5"}, "some extra parameter", TestName="SeveralParams")]
public void Parse_InvalidParametersNumber_ThrowsException(params string[] args)
{
    new ParametersParser(args).Parse();
}

edited May 23 '17 at 10:28

Community

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answered May 28 '14 at 17:49

GoetzOnline

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You link to a resharper issue, while the problem seems to be in nunit ... in any case, seems like resharper solved the problem – Noctis Oct 03 '14 at 05:35
1

Doing this with `new[] { ... }` where the array is of strings gives the error CS0182 as referenced by the OP above. Integer types seem to work properly. – Brandon Feb 23 '15 at 18:21

score 0 · Answer 3 · answered Jun 25 '20 at 06:32

Although I don't recommend this approach,

yet here is one more way to pass a single argument to a params array by using a dummy object parameter before the params parameter.

See the example below:

[ExpectedException(typeof(ParametersParseException))]
[TestCase(null, "param1")]
[TestCase(null, "param1", "param2")]
[TestCase(null, "param1", "param2", "param3", "optParam4", "optParam5", "some extra parameter")]
public void Parse_InvalidParametersNumber_ThrowsException(object _, params string[] args)
{
    new ParametersParser(args).Parse();
}

PS A better way to accomplish that would be using the TestCaseSource attribute.

Passing single value to params argument in NUnit TestCase

3 Answers3

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