[英]NUnit assertion that a certain exception is not thrown
NUnit具有這些:
Exception Assert.Throws<TActual>(TestDelegate) // code must throw a TActual
void Assert.DoesNotThrow(TestDelegate) // code mustn't throw anything
它沒有這個:
Exception Assert.DoesNotThrow<TActual>(TestDelegate) // code musn't throw a TActual, but
// is allowed to throw anything else
我該如何創建它,或使用約束機制來做到這一點?
也許可以這樣實現:
public static class CustomAssert
{
public static void DoesNotThrow<T>(TestDelegate code) where T : Exception
{
DoesNotThrow<T>(code, string.Empty, null);
}
public static void DoesNotThrow<T>(TestDelegate code, string message, params object[] args) where T : Exception
{
Assert.That(code, new ThrowsNotExceptionConstraint<T>(), message, args);
}
}
public class ThrowsNotExceptionConstraint<T> : ThrowsExceptionConstraint where T : Exception
{
public override string Description
{
get { return string.Format("throw not exception {0}", typeof(T).Name); }
}
public override ConstraintResult ApplyTo<TActual>(TActual actual)
{
var result = base.ApplyTo<TActual>(actual);
return new ThrowsNotExceptionConstraintResult<T>(this, result.ActualValue as Exception);
}
protected override object GetTestObject<TActual>(ActualValueDelegate<TActual> del)
{
return new TestDelegate(() => del());
}
class ThrowsNotExceptionConstraintResult<T> : ConstraintResult where T : Exception
{
public ThrowsNotExceptionConstraintResult(ThrowsNotExceptionConstraint<T> constraint, Exception caughtException)
: base(constraint, caughtException, !(caughtException is T)) { }
public override void WriteActualValueTo(MessageWriter writer)
{
if (this.Status == ConstraintStatus.Failure)
writer.Write("throws exception {0}", typeof(T).Name);
else
base.WriteActualValueTo(writer);
}
}
}
並稱它為
CustomAssert.DoesNotThrow<TException>(() => { throw new TException(); });
我沒有使用NUnit,所以也許有更好的方法。
如果找不到任何更清潔的解決方案,則可以執行以下操作。
[Test]
public void TestThatMyExceptionWillNotBeThrown()
{
try
{
TheMethodToTest();
// if the method did not throw any exception, the test passes
Assert.That(true);
}
catch(Exception ex)
{
// if the thrown exception is MyException, the test fails
Assert.IsFalse(ex is MyException);
}
}
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