feat: finally nailed down phases 1-4

MLXServerTests/Server/ChatViewModelTests.swift

@@ -0,0 +1,46 @@
+import XCTest
+@testable import MLX_Server
+
+@MainActor
+final class ChatViewModelTests: XCTestCase {
+    func testGemmaChatViewModelSendProducesAssistantReply() async throws {
+        let modelManager = ModelManager()
+        let config = try XCTUnwrap(ModelConfig.resolve("gemma"))
+        await modelManager.loadModel(config)
+        defer { modelManager.unloadModel() }
+
+        XCTAssertTrue(modelManager.isReady)
+
+        let viewModel = ChatViewModel(modelManager: modelManager)
+        viewModel.inputText = "Say hello in one word."
+        viewModel.send()
+
+        XCTAssertTrue(viewModel.isGenerating)
+
+        try await waitUntil(timeoutSeconds: 15) {
+            !viewModel.isGenerating
+        }
+
+        XCTAssertEqual(viewModel.conversation.messages.count, 2)
+        XCTAssertEqual(viewModel.conversation.messages[0].role, .user)
+        XCTAssertEqual(viewModel.conversation.messages[0].content, "Say hello in one word.")
+        XCTAssertEqual(viewModel.conversation.messages[1].role, .assistant)
+        XCTAssertFalse(viewModel.conversation.messages[1].sessionContent.isEmpty)
+        XCTAssertGreaterThan(viewModel.promptTokens, 0)
+    }
+
+    private func waitUntil(
+        timeoutSeconds: TimeInterval,
+        intervalNanoseconds: UInt64 = 100_000_000,
+        condition: @escaping @MainActor () -> Bool
+    ) async throws {
+        let deadline = Date().addingTimeInterval(timeoutSeconds)
+        while Date() < deadline {
+            if condition() {
+                return
+            }
+            try await Task.sleep(nanoseconds: intervalNanoseconds)
+        }
+        XCTFail("Condition not met before timeout")
+    }
+}