Fixed unit test cases and formatting

core-kotlin/src/main/kotlin/com/baeldung/filesystem/FileWriter.kt

@@ -5,13 +5,13 @@ import java.io.File
 class FileWriter {
 
     fun writeFileUsingPrintWriter(fileName: String, fileContent: String) =
-        File(fileName).printWriter().use { out -> out.println(fileContent) }
+            File(fileName).printWriter().use { out -> out.print(fileContent) }
 
     fun writeFileUsingBufferedWriter(fileName: String, fileContent: String) =
-        File(fileName).bufferedWriter().use { out -> out.write(fileContent) }
+            File(fileName).bufferedWriter().use { out -> out.write(fileContent) }
 
     fun writeFileDirectly(fileName: String, fileContent: String) =
-        File(fileName).writeText(fileContent)
+            File(fileName).writeText(fileContent)
 
     fun writeFileDirectlyAsBytes(fileName: String, fileContent: String) =
             File(fileName).writeBytes(fileContent.toByteArray())

core-kotlin/src/test/kotlin/com/baeldung/filesystem/FileWriterTest.kt

@@ -1,6 +1,8 @@
 package com.baeldung.filesystem
 
 import org.junit.jupiter.api.Test
+import java.io.File
+import kotlin.test.assertEquals
 
 internal class FileWriterTest {
 
@@ -13,21 +15,29 @@ internal class FileWriterTest {
     @Test
     fun whenWrittenWithPrintWriter_thenCorrect() {
         fileWriter.writeFileUsingPrintWriter(fileName, fileContent)
+
+        assertEquals(fileContent, File(fileName).readText())
     }
 
     @Test
     fun whenWrittenWithBufferedWriter_thenCorrect() {
         fileWriter.writeFileUsingBufferedWriter(fileName, fileContent)
+
+        assertEquals(fileContent, File(fileName).readText())
     }
 
     @Test
     fun whenWrittenDirectly_thenCorrect() {
         fileWriter.writeFileDirectly(fileName, fileContent)
+
+        assertEquals(fileContent, File(fileName).readText())
     }
 
     @Test
     fun whenWrittenDirectlyAsBytes_thenCorrect() {
         fileWriter.writeFileDirectlyAsBytes(fileName, fileContent)
+
+        assertEquals(fileContent, File(fileName).readText())
     }
 
 }