add swiftUI code

iOS-SwiftUI-Code/GRDB.swift-6.29.3/Tests/GRDBTests/DatabasePoolFunctionTests.swift

@@ -0,0 +1,23 @@
+import XCTest
+import GRDB
+
+class DatabasePoolFunctionTests: GRDBTestCase {
+    
+    func testFunctionIsSharedBetweenWriterAndReaders() throws {
+        dbConfiguration.prepareDatabase { db in
+            db.add(function: DatabaseFunction("function1", argumentCount: 1, pure: true) { (dbValues: [DatabaseValue]) in
+                return dbValues[0]
+            })
+            
+        }
+        let dbPool = try makeDatabasePool()
+        
+        try dbPool.write { db in
+            try db.execute(sql: "CREATE TABLE items (text TEXT)")
+            try db.execute(sql: "INSERT INTO items (text) VALUES (function1('a'))")
+        }
+        try dbPool.read { db in
+            XCTAssertEqual(try String.fetchOne(db, sql: "SELECT function1(text) FROM items")!, "a")
+        }
+    }
+}