Does XCTest supports Generics?

[ganaraj-savant]

If I run below test, it succeeds, all test cases are marked green:

import XCTest


class SomeTestCaseSon: XCTestCase {
    override func setUp() {
        super.setUp()
    }

    func testblablblblablba() {
    }

}

class SomeTestCase: XCTestCase {
    override func setUp() {
        super.setUp()
    }

    func testblablblblablba() {
    }
}

class SomeGenericTestCase<T:NSObject>: XCTestCase {
    override func setUp() {
        super.setUp()
    }

    func testblablblblablba() {

    }
}

But when I try with the below code, the test succeeds but the test cases are not marked green. Also breakpoint won't work.

class SomeGenericTestCase<T: Decodable>: XCTestCase {
    override func setUp() {
        super.setUp()
    }

    func testblablblblablba() {

    }
}


class SomeTestCaseGeneral: SomeGenericTestCase<NSObject> {
    override func setUp() {
        super.setUp()
    }

    override func testblablblblablba() {
    }
}

Thanks in advance!

[xwu (Xiaodi Wu)]

This may be relevant:

XCTest is not testing a test methods defined in a generic subclass of XCTestCase

Our team just discovered that Darwin's XCTest is not testing a test methods that are part of a test case which is a generic subclass of XCTestCase. Those methods are displayed in the Test Navigator and can be executed manually but are not executed by Product->Tests or command line tools on CI. On the beginning I was thinking that the problem is part of discovery tool but those test methods are displayed in the Test Navigator so maybe it's something else. class MockGenerator {} class CustomTe…

What version of Swift and which OS are you using?

[ganaraj-savant]

Swift 5
Running on iPhone 14 Simulator with iOS version 16.2

[smontgomery (Stuart Montgomery)]

This feature is only expected to work for specialized subclasses of generic subclasses of XCTestCase. So for example, in the following code:

struct Foo { ... }

class Parent<T>: XCTestCase { ... }
class Child: Parent<Foo> { ... }

only the test class Child and the test methods it contains will be run, since it is a subclass of Parent which specializes the generic T type to be the concrete type Foo.

It is not possible to run Parent on its own, because there is no information about what specific type to use for T and XCTest needs that in order to instantiate an instance of Parent.