update to new testing syntax

Author: kostiakoval

Fixtures/SwiftTesting/SingleTarget/Tests/Foo/Test.swift

@@ -8,12 +8,10 @@ class SimpleGetTests: XCTestCase {
     }
 }
 
-#if os(Linux)
-extension SimpleGetTests: XCTestCaseProvider {
-    var allTests : [(String, () throws -> Void)] {
+extension SimpleGetTests {
+    static var allTests : [(String, SimpleGetTests -> () throws -> Void)]  {
         return [
             ("testGetRequestStatusCode", testGetRequestStatusCode),
         ]
     }
 }
-#endif

Fixtures/SwiftTesting/SingleTarget/Tests/LinuxMain.swift

@@ -3,5 +3,5 @@ import XCTest
 @testable import Footest
 
 XCTMain([
-    SimpleGetTests(),
+    testCase(SimpleGetTests.allTests),
 ])