test: Use XCTestExpectation for FlushTests (#5903)

Replace DispatchGroup with XCTextExpectation in
SentryHttpTransportFlushIntegrationTests.

Author: philipphofmann

Tests/SentryTests/Networking/SentryHttpTransportFlushIntegrationTests.swift

@@ -98,48 +98,58 @@ final class SentryHttpTransportFlushIntegrationTests: XCTestCase {
         for _ in 0..<30 {
             sut.send(envelope: SentryEnvelope(event: Event()))
         }
-        // Wait until the dispath queue drains to confirm the envelope is stored
+        // Wait until the dispatch queue drains to confirm the envelope is stored
         waitForEnvelopeToBeStored(dispatchQueueWrapper)
         requestManager.returnResponse(response: HTTPURLResponse())
 
-        let initialFlushCallGroup = DispatchGroup()
-        let ensureFlushingGroup = DispatchGroup()
+        let initialFlushCallExpectation = XCTestExpectation(description: "Initial flush call should succeed")
+        initialFlushCallExpectation.assertForOverFulfill = true
+
+        let ensureFlushingExpectation = XCTestExpectation(description: "Ensure flushing is called")
+        ensureFlushingExpectation.assertForOverFulfill = true
+
         let ensureFlushingQueue = DispatchQueue(label: "First flushing")
 
         sut.setStartFlushCallback {
-            ensureFlushingGroup.leave()
+            ensureFlushingExpectation.fulfill()
         }
 
-        initialFlushCallGroup.enter()
-        ensureFlushingGroup.enter()
         ensureFlushingQueue.async {
             XCTAssertEqual(.success, sut.flush(flushTimeout), "Initial call to flush should succeed")
-            initialFlushCallGroup.leave()
+            initialFlushCallExpectation.fulfill()
         }
 
         // Ensure transport is flushing.
-        ensureFlushingGroup.waitWithTimeout()
+        wait(for: [ensureFlushingExpectation], timeout: 10.0)
 
         // Now the transport should also have left the synchronized block, and the
         // flush should return immediately.
 
-        let parallelFlushCallsGroup = DispatchGroup()
+        let loopCount = 2
+        let parallelFlushCallsExpectation = XCTestExpectation(description: "Parallel flush calls should return immediately")
+        parallelFlushCallsExpectation.expectedFulfillmentCount = loopCount
+        parallelFlushCallsExpectation.assertForOverFulfill = true
+
         let initiallyInactiveQueue = DispatchQueue(label: "testFlush_CalledMultipleTimes_ImmediatelyReturnsFalse", qos: .userInitiated, attributes: [.concurrent, .initiallyInactive])
-        for _ in 0..<2 {
-            parallelFlushCallsGroup.enter()
+        for _ in 0..<loopCount {
+
             initiallyInactiveQueue.async {
                 for _ in 0..<10 {
                     XCTAssertEqual(.alreadyFlushing, sut.flush(flushTimeout), "Flush should have returned immediately")
                 }
 
-                parallelFlushCallsGroup.leave()
+                parallelFlushCallsExpectation.fulfill()
             }
         }
 
         initiallyInactiveQueue.activate()
-        parallelFlushCallsGroup.waitWithTimeout()
+        wait(for: [parallelFlushCallsExpectation], timeout: 10.0)
+
         requestManager.responseDispatchGroup.leave()
-        initialFlushCallGroup.waitWithTimeout()
+
+        // The initial call to flush is blocking and will take some time to finish.
+        // Therefore, we wait at the end of the test.
+        wait(for: [initialFlushCallExpectation], timeout: 10.0)
     }
 
     // We use the test name as part of the DSN to ensure that each test runs in isolation.