add swiftUI code

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

@@ -0,0 +1,29 @@
+import XCTest
+import GRDB
+
+class ValueObservationMapTests: GRDBTestCase {
+    func testMap() throws {
+        let valueObservation = ValueObservation
+            .trackingConstantRegion(Table("t").fetchCount)
+            .map { "\($0)" }
+        
+        try assertValueObservation(
+            valueObservation,
+            records: ["0", "1", "2"],
+            setup: { db in
+                try db.execute(sql: "CREATE TABLE t(id INTEGER PRIMARY KEY AUTOINCREMENT)")
+        },
+            recordedUpdates: { db in
+                try db.execute(sql: "INSERT INTO t DEFAULT VALUES")
+                try db.execute(sql: "INSERT INTO t DEFAULT VALUES")
+        })
+    }
+    
+    func testMapPreservesConfiguration() {
+        var observation = ValueObservation.trackingConstantRegion { _ in }
+        observation.requiresWriteAccess = true
+        
+        let mappedObservation = observation.map { _ in }
+        XCTAssertEqual(mappedObservation.requiresWriteAccess, observation.requiresWriteAccess)
+    }
+}