KTLN-709 Rename a file in Kotlin (#819)

Author: polomos

core-kotlin-modules/core-kotlin-io/src/test/kotlin/com/baeldung/renameFile/RenameFileUnitTest.kt

@@ -0,0 +1,73 @@
+package com.baeldung.renameFile
+
+import org.assertj.core.api.Assertions.assertThat
+import org.assertj.core.api.Assertions.fail
+import org.junit.jupiter.api.Test
+import java.nio.file.Files
+import java.nio.file.Paths
+import java.nio.file.StandardCopyOption
+
+class RenameFileUnitTest {
+
+    @Test
+    fun `when using renameTo, then file is renamed`() {
+        val oldFilePath = Paths.get("src/test/resources/oldFile.txt")
+        val newFilePath = Paths.get("src/test/resources/newFile.txt")
+
+        val oldFile = oldFilePath.toFile()
+        oldFile.writeText("Hello Kotlin")
+
+        val newFile = newFilePath.toFile()
+
+        if (oldFile.renameTo(newFile)) {
+            assertThat(newFile.exists()).isTrue()
+        } else {
+            fail("Failed to rename file.")
+        }
+        //cleanup
+        newFile.delete()
+    }
+
+@Test
+fun `when renaming, checks on files succeed`() {
+    val oldFilePath = Paths.get("src/test/resources/oldFile.txt")
+    val newFilePath = Paths.get("src/test/resources/newFile.txt")
+
+    val oldFile = oldFilePath.toFile()
+    oldFile.writeText("Hello Kotlin")
+
+    val newFile = newFilePath.toFile()
+
+    if (oldFile.exists()) {
+        if (newFile.exists()) {
+            fail("A file with the new name already exists.")
+        } else {
+            if (oldFile.renameTo(newFile)) {
+                assertThat(newFile.exists()).isTrue()
+            } else {
+                fail("Fail rename failed")
+            }
+        }
+    } else {
+        fail("The old file does not exist.")
+    }
+    //cleanup
+    newFile.delete()
+}
+
+    @Test
+    fun `when using move, then file is renamed`() {
+        val oldFilePath = Paths.get("src/test/resources/oldFile.txt")
+        val newFilePath = Paths.get("src/test/resources/newFile.txt")
+
+        val oldFile = oldFilePath.toFile()
+        oldFile.writeText("Hello Kotlin")
+
+        Files.move(oldFilePath, newFilePath, StandardCopyOption.REPLACE_EXISTING)
+        val newFile = newFilePath.toFile()
+        assertThat(newFile.exists()).isTrue()
+        //cleanup
+        newFile.delete()
+    }
+
+}