Write a failing test

Tests/OpenAITests/ServerSentEventsStreamInterpreterTests.swift

@@ -86,18 +86,26 @@ struct ServerSentEventsStreamInterpreterTests {
     }
     
     // Chunk with 3 objects. I captured it from a real response. It's a very short response that contains just "Hi"
-    private func chatCompletionChunk() -> Data {
+    static func chatCompletionChunk() -> Data {
         "data: {\"id\":\"chatcmpl-AwnboO5ZnaUyii9xxC5ZVmM5vGark\",\"object\":\"chat.completion.chunk\",\"created\":1738577084,\"model\":\"gpt-4-0613\",\"service_tier\":\"default\",\"system_fingerprint\":\"sysfig\",\"choices\":[{\"index\":0,\"delta\":{\"role\":\"assistant\",\"content\":\"\",\"refusal\":null},\"logprobs\":null,\"finish_reason\":null}]}\n\ndata: {\"id\":\"chatcmpl-AwnboO5ZnaUyii9xxC5ZVmM5vGark\",\"object\":\"chat.completion.chunk\",\"created\":1738577084,\"model\":\"gpt-4-0613\",\"service_tier\":\"default\",\"system_fingerprint\":\"sysfig\",\"choices\":[{\"index\":0,\"delta\":{\"content\":\"Hi\"},\"logprobs\":null,\"finish_reason\":null}]}\n\ndata: {\"id\":\"chatcmpl-AwnboO5ZnaUyii9xxC5ZVmM5vGark\",\"object\":\"chat.completion.chunk\",\"created\":1738577084,\"model\":\"gpt-4-0613\",\"service_tier\":\"default\",\"system_fingerprint\":\"sysfig\",\"choices\":[{\"index\":0,\"delta\":{},\"logprobs\":null,\"finish_reason\":\"stop\"}]}\n\n".data(using: .utf8)!
     }
     
+    private func chatCompletionChunk() -> Data {
+        type(of: self).chatCompletionChunk()
+    }
+    
     private func chatCompletionChunkWithComment() -> Data {
         ": OPENROUTER PROCESSING\n\ndata: {\"id\":\"chatcmpl-AwnboO5ZnaUyii9xxC5ZVmM5vGark\",\"object\":\"chat.completion.chunk\",\"created\":1738577084,\"model\":\"gpt-4-0613\",\"service_tier\":\"default\",\"system_fingerprint\":\"sysfig\",\"choices\":[{\"index\":0,\"delta\":{\"role\":\"assistant\",\"content\":\"\",\"refusal\":null},\"logprobs\":null,\"finish_reason\":null}]}\n\n".data(using: .utf8)!
     }
     
-    private func chatCompletionChunkTermination() -> Data {
+    static func chatCompletionChunkTermination() -> Data {
         "data: [DONE]\n\n".data(using: .utf8)!
     }
     
+    private func chatCompletionChunkTermination() -> Data {
+        type(of: self).chatCompletionChunkTermination()
+    }
+    
     // Copied from an actual reponse that was an input to inreptreter
     private func chatCompletionError() -> Data {
         "{\n    \"error\": {\n        \"message\": \"The model `o3-mini` does not exist or you do not have access to it.\",\n        \"type\": \"invalid_request_error\",\n        \"param\": null,\n        \"code\": \"model_not_found\"\n    }\n}\n".data(using: .utf8)!

Tests/OpenAITests/StreamingSessionIntegrationTests.swift

+//
+//  StreamingSessionIntegrationTests.swift
+//  OpenAI
+//
+//  Created by Oleksii Nezhyborets on 31.03.2025.
+//
+
+import XCTest
+@testable import OpenAI
+
+final class StreamingSessionIntegrationTests: XCTestCase {
+    private enum Call {
+        case content
+        case complete
+    }
+    
+    private let urlSessionFactory = MockURLSessionFactory()
+    private let streamInterpreter = ServerSentEventsStreamInterpreter<ChatStreamResult>(parsingOptions: [])
+    private var calls: [Call] = []
+    private lazy var expectation: XCTestExpectation = {
+        let expectation = self.expectation(description: "3 content and 1 finish happened")
+        expectation.expectedFulfillmentCount = 4
+        return expectation
+    }()
+    
+    private lazy var streamingSession = StreamingSession(
+        urlSessionFactory: urlSessionFactory,
+        urlRequest: .init(url: .init(string: "/")!),
+        interpreter: streamInterpreter,
+        sslDelegate: nil,
+        middlewares: [],
+        onReceiveContent: { _, _ in
+            Task {
+                await MainActor.run {
+                    self.calls.append(.content)
+                    self.expectation.fulfill()
+                }
+            }
+        },
+        onProcessingError: { _, _ in },
+        onComplete: { _,_ in
+            Task {
+                await MainActor.run {
+                    self.calls.append(.complete)
+                    self.expectation.fulfill()
+                }
+            }
+        }
+    )
+
+    @MainActor
+    func testCompleteCalledAfterAllEvents() {
+        _ = streamingSession
+        let cancellable = streamingSession.makeSession()
+        
+        let dataEvent = ServerSentEventsStreamInterpreterTests.chatCompletionChunk()
+        streamInterpreter.processData(dataEvent)
+        
+        let doneEvent = ServerSentEventsStreamInterpreterTests.chatCompletionChunkTermination()
+        streamInterpreter.processData(doneEvent)
+        
+        let urlSession = urlSessionFactory.urlSession
+        urlSession.delegate!.urlSession(urlSession, task: DataTaskMock(), didCompleteWithError: nil)
+        
+        wait(for: [expectation])
+        
+        XCTAssertEqual(calls[0], .content)
+        XCTAssertEqual(calls[1], .content)
+        XCTAssertEqual(calls[2], .content)
+        XCTAssertEqual(calls[3], .complete)
+        cancellable.invalidateAndCancel() // just to hold a reference
+    }
+
+}