Additional Considerations for Swift on Linux

When running on the Objective-C runtime, XCTest is able to find all of your tests by simply asking the runtime for the subclasses of XCTestCase. It then finds the methods that start with the string test. This functionality is not currently present when running on the Swift runtime. Therefore, you must currently provide an additional property, conventionally named allTests, in your XCTestCase subclass. This method lists all of the tests in the test class. The rest of your test case subclass still contains your test methods.

class TestNSURL : XCTestCase {
    static var allTests = {
        return [
            ("test_URLStrings", test_URLStrings),
            ("test_fileURLWithPath_relativeToURL", test_fileURLWithPath_relativeToURL),
            ("test_fileURLWithPath", test_fileURLWithPath),
            ("test_fileURLWithPath_isDirectory", test_fileURLWithPath_isDirectory),
            // Other tests go here

    func test_fileURLWithPath_relativeToURL() {
        // Write your test here. Most of the XCTAssert macros you are familiar with are available.
        XCTAssertTrue(theBestNumber == 42, "The number is wrong")

    // Other tests go here

Also, this version of XCTest does not use the external test runner binary. Instead, create your own executable which links In your main.swift, invoke the XCTMain function with an array of the tests from the XCTestCase subclasses that you wish to run, wrapped by the testCase helper function. For example:

XCTMain([testCase(TestNSString.allTests), testCase(TestNSArray.allTests), testCase(TestNSDictionary.allTests)])

We are currently investigating ideas on how to make these additional steps for test discovery automatic when running on the Swift runtime.

Command Line Usage

The XCTMain function does not return, and will cause your test app to exit with either 0 for success or 1 for failure. Certain command line arguments can be used to modify the test runner behavior:

  • A particular test or test case can be selected to execute. For example:
$ ./FooTests Tests.FooTestCase/testFoo  # Run a single test case
$ ./FooTests Tests.FooTestCase          # Run all the tests in FooTestCase
  • Tests can be listed, instead of executed.
$ ./FooTests --list-tests
Listing 4 tests in FooTests.xctest:


$ ./FooTests --dump-tests-json
{"tests":[{"tests":[{"tests":[{"name":"testFoo"},{"name":"testBar"}],"name":"Tests.FooTestCase"},{"tests":[{"name":"test123"}],"name":"Tests.BarTestCase"}],"name":"Tests.xctest"}],"name":"All tests"}