Refactor save return type without Either

src/test/scala/db/DBServiceSpec.scala

@@ -4,6 +4,7 @@ import cats.effect.unsafe.implicits.global
 import org.scalatest.funsuite.AnyFunSuite
 import org.scalatest.matchers.should.Matchers
 
+import java.io.IOException
 import java.time.format.DateTimeFormatter
 import java.time.{LocalDate, LocalDateTime}
 
@@ -32,4 +33,26 @@ class DBServiceSpec extends AnyFunSuite with Matchers {
 
     lines.length shouldBe 2142
   }
+
+  test("DBService.save should return correct result") {
+    val dbService = DBService.of.unsafeRunSync()
+    val fileName = "testFile.txt"
+    val fileContent = "test content..."
+
+    dbService.save(fileName, fileContent).unsafeRunSync() shouldEqual fileName
+  }
+
+  test("DBService.save returns error on invalid file name") {
+    val dbService = DBService.of.unsafeRunSync()
+    val fileName = "/invalid/file/name"
+    val fileContent = "test content..."
+
+    val result = dbService.save(fileName, fileContent).attempt.unsafeRunSync()
+
+    result match {
+      case Left(e) =>
+        assert(e.isInstanceOf[IOException])
+      case Right(_) => fail("Expected failure did not occur")
+    }
+  }
 }