diff --git a/legacy/core/src/test/java/com/fsck/k9/helper/FileHelperTest.kt b/legacy/core/src/test/java/com/fsck/k9/helper/FileHelperTest.kt
new file mode 100644
index 00000000000..5b5d3a4b3b0
--- /dev/null
+++ b/legacy/core/src/test/java/com/fsck/k9/helper/FileHelperTest.kt
@@ -0,0 +1,68 @@
+package com.fsck.k9.helper
+
+import assertk.assertThat
+import assertk.assertions.isEqualTo
+import assertk.assertions.isFalse
+import assertk.assertions.isNotEqualTo
+import assertk.assertions.isTrue
+import java.io.File
+import kotlin.test.Test
+import org.junit.Rule
+import org.junit.rules.TemporaryFolder
+
+class FileHelperTest {
+
+    @Rule
+    @JvmField
+    val tempFolder = TemporaryFolder()
+
+    @Test
+    fun `touchFile should create file`() {
+        val parent = tempFolder.newFolder("parent")
+
+        FileHelper.touchFile(parent, "FileName")
+
+        assertThat(File(parent, "FileName").exists()).isTrue()
+    }
+
+    @Test
+    fun `touchFile should change file modification time`() {
+        val parent = tempFolder.newFolder("parent")
+        val lastModified = 12345L
+        val file = File(parent, "FileName")
+        file.createNewFile()
+        file.setLastModified(lastModified)
+
+        FileHelper.touchFile(parent, "FileName")
+
+        assertThat(file.lastModified()).isNotEqualTo(lastModified)
+    }
+
+    @Test
+    fun `renameOrMoveByCopying should move file when destination does not exist`() {
+        val source = tempFolder.newFile("source")
+        val destination = File(tempFolder.root, "destination")
+        val sourceContent = "content"
+        source.writeText(sourceContent)
+
+        FileHelper.renameOrMoveByCopying(source, destination)
+
+        assertThat(source.exists()).isFalse()
+        assertThat(destination.exists()).isTrue()
+        assertThat(destination.readText()).isEqualTo(sourceContent)
+    }
+
+    @Test
+    fun `renameOrMoveByCopying should move file when destination exists`() {
+        val source = tempFolder.newFile("source")
+        val destination = tempFolder.newFile("destination")
+        val sourceContent = "content"
+        source.writeText(sourceContent)
+
+        FileHelper.renameOrMoveByCopying(source, destination)
+
+        assertThat(source.exists()).isFalse()
+        assertThat(destination.exists()).isTrue()
+        assertThat(destination.readText()).isEqualTo(sourceContent)
+    }
+}