Fix concurrency thread-safe exception

Tests/SwiftMathTests/ConcurrencyThreadsafeTests.swift

@@ -1,8 +1,47 @@
 //
-//  File.swift
+//  ConcurrencyThreadsafeTests.swift
 //  
 //
 //  Created by Peter Tang on 26/9/2023.
 //
 
-import Foundation
+import XCTest
+@testable import SwiftMath
+
+final class ConcurrencyThreadsafeTests: XCTestCase {
+    
+    private let executionQueue = DispatchQueue(label: "com.swiftmath.concurrencytests", attributes: .concurrent)
+    private let executionGroup = DispatchGroup()
+    
+    let totalCases = 20
+    var testCount = 0
+    
+    func testSwiftMathConcurrentScript() throws {
+        for caseNumber in 0 ..< totalCases {
+            helperConcurrency(caseNumber, in: executionGroup, on: executionQueue) {
+                let result1 = getInterElementSpaces()
+                let result2 = MTMathAtomFactory.delimValueToName
+                let result3 = MTMathAtomFactory.accentValueToName
+                let result4 = MTMathAtomFactory.textToLatexSymbolName
+                XCTAssertNotNil(result1)
+                XCTAssertNotNil(result2)
+                XCTAssertNotNil(result3)
+                XCTAssertNotNil(result4)
+            }
+        }
+        executionGroup.notify(queue: .main) { [weak self] in
+            // print("All test cases completed: \(self?.testCount ?? 0)")
+        }
+        executionGroup.wait()
+    }
+    func helperConcurrency(_ count: Int, in group: DispatchGroup, on queue: DispatchQueue, _ testClosure: @escaping () -> (Void)) {
+        let workitem = DispatchWorkItem {
+            testClosure()
+        }
+        workitem.notify(queue: .main) { [weak self] in
+            self?.testCount += 1
+        }
+        queue.async(group: group, execute: workitem)
+    }
+
+}