[SR-460] API incompatibility of XCTestCase setUp() and tearDown() methods

[briancroom]

Previous ID	SR-460
Radar	None
Original Reporter	@briancroom
Type	Bug
Status	Closed
Resolution	Done

Additional Detail from JIRA

Votes	1
Component/s	XCTest
Labels	Bug
Assignee	@briancroom
Priority	Medium

md5: d4d2b61860ed289302e1fd98c142f4e9

Issue Description:

The following trivial test case, taken nearly verbatim from Xcode's "Unit Test Case Class" file template, builds and runs using Apple XCTest, but fails to compile using `swift-corelibs-xctest`:

import XCTest

class Test: XCTestCase {
    var allTests: [(String, () -> Void)] { return [("testExample", testExample)] }

    override func setUp() {
        super.setUp()
    }

    override func tearDown() {
        super.tearDown()
    }

    func testExample() {
        XCTAssertEqual(1, 1)
    }
}

The errors produced are:

/home/osboxes/swift/LetsTryXCTest/Sources/Test.swift:6:19: error: method does not override any method from its superclass
    override func setUp() {
    ~~~~~~~~      ^
/home/osboxes/swift/LetsTryXCTest/Sources/Test.swift:10:19: error: method does not override any method from its superclass
    override func tearDown() {
    ~~~~~~~~      ^
/home/osboxes/swift/LetsTryXCTest/Sources/Test.swift:7:9: error: 'super' members cannot be referenced in a root class
        super.setUp()
        ^
/home/osboxes/swift/LetsTryXCTest/Sources/Test.swift:11:9: error: 'super' members cannot be referenced in a root class
        super.tearDown()
        ^

The reason for this is that when building with Apple XCTest, the `setUp` and `tearDown` methods are defined on the `XCTest` base class and thus must include the `override` modifier when used in client code, whereas `swift-corelibs-xctest` defines them in the `XCTestCase` protocol (or should, anyway. See [this PR](#26

While I am generally a big fan of the idea of defining `XCTestCase` as a protocol instead of a class that must be derived from, I don't think there is any way to maintain source-level compatibility for users of the framework without converting `XCTestCase` to be a class, thus allowing these test lifecycle methods to be overridden.

[modocache]

I was just thinking this the other day. I agree that a truly compatible XCTest would allow consumers to call super.setUp() and super.tearDown().

I suppose one "workaround" is not calling super in tests that are meant to be run on both platforms. This hardly seems like a long-term solution, though.

Fun fact: you point out that the file templates from Xcode call super, but the documentation from Apple's XCTestCase.h does not. My theory is that this is a bug in the documentation:

/*!
 * @class XCTestCase
 * XCTestCase is a concrete subclass of XCTest...
 * ...
 * Test method implementations usually contain assertions that must be verified
 * for the test to pass, for example:
 
    @interface MathTest : XCTestCase {
    @private
        float f1;
        float f2;
    }
    - (void)testAddition;
    @end
    @implementation MathTest
    - (void)setUp
    {
        f1 = 2.0;
        f2 = 3.0;
    }
    - (void)testAddition
    {
        XCTAssertTrue (f1 + f2 == 5.0);
    }
    @end
 */
@interface XCTestCase : XCTest
// ....

[briancroom]

@modocache The real kicker is that first pair of errors - the `override` keyword is required for Apple's XCTest and prohibited for Corelibs XCTest, since it isn't overriding anything. No workaround available besides writing two separate definitions with conditional compilation..

[briancroom]

This is resolved now that #40 has been merged!