Does XCTest supports Generics?

Using Swift
, ,
1

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!

2

This may be relevant:

What version of Swift and which OS are you using?

3

Swift 5
Running on iPhone 14 Simulator with iOS version 16.2

4

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.

3 Likes