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?

Answer 1

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

Answer 2

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();
}