rspec/rules/S3431/csharp/rule.adoc

It should be clear to a casual reader what code a test is testing and what results are expected. Unfortunately, that's not usually the case with the ``++[ExpectedException]++`` attribute since an exception could be thrown from almost any line in the method.


This rule detects MSTest and NUnit ``++ExpectedException++`` attribute.


== Noncompliant Code Example

----
[TestMethod]
[ExpectedException(typeof(ArgumentNullException))]  // Noncompliant
public void TestNullArg()
{
  //...
}
----


== Compliant Solution

----
[TestMethod]
public void TestNullArg()
{
  bool callFailed = false;
  try
  {
    //...
  }
  catch (ArgumentNullException)
  {
    callFailed = true;
  }
  Assert.IsTrue(callFailed, "Expected call to MyMethod to fail with ArgumentNullException");
}
----

or


----
[TestMethod]
public void TestNullArg()
{
  Assert.ThrowsException<ArgumentNullException>(() => /*...*/);
}
----


== Exceptions

This rule ignores one-line test methods, since it is obvious in such methods where the exception is expected to be thrown.