I'm writing Cocoa unit tests using XCTest and recently used XCTAssertThrows for the first time. That's pretty cool, but I want to make it even better with XCTAssertThrowsSpecific and requiring a certain exception.
Here is an example test:
-(void)testShortPassword {
XCTAssertThrows([user storePassword:@"abc"],@"Expect exception for short pw");
}
And on my user class I have the following code:
-(void)storePassword:(NSString*)password {
NSCAssert(password.length > 6, @"Password must be longer than 6 characters");
// go on to store the password on the keychain
}
Keeping in mind that Cocoa in general shies away from using exceptions (so it might be better to return an error, and show UI in the preceding example, etc.) How do I throw an exception in a manner that can be caught by XCTAssertThrowsSpecific
? How do I specify that in XCTAssertThrowsSpecific(expression, specificException, format...)
?
You should only use exceptions for exceptional cases, not for error handling and flow control
Having said that, here's how you use XCTAssertThrowsSpecific
:
XCTAssertThrowsSpecific
expects the specific class of the exception as the second parameter. NSCAssert
throws an NSException
. To test for that, use
XCTAssertThrowsSpecific([object methodThatShouldThrow], NSException, @"should throw an exception");
Now, that won't help much, because it's likely that every exception is an NSException
or a subclass thereof.
NSException
s have a name
property that determines the type of the exception. In case of NSCAssert
this is NSInternalInconsistencyException
. To test for that, use XCTAssertThrowsSpecificNamed
XCTAssertThrowsSpecificNamed(
[object methodThatShouldThrow],
NSException,
NSInternalInconsistencyException,
@"should throw NSInternalInconsistencyException"
);