Replace functions in FileUtilsTest with ones from kotlin-stdlib (#2943)

Author: veyndan

app/src/test/kotlin/fr/free/nrw/commons/utils/FileUtilsTest.kt

@@ -10,7 +10,7 @@ class FileUtilsTest {
     @Test
     fun deleteFile() {
         val file = File.createTempFile("testfile", "")
-        writeToFile(file, "Hello, World")
+        file.writeText("Hello, World")
 
         assertEquals(true, file.exists())
         assertEquals(true, FileUtils.deleteFile(file))
@@ -23,40 +23,22 @@ class FileUtilsTest {
 
         assertEquals(
                 "907d14fb3af2b0d4f18c2d46abe8aedce17367bd",
-                fileUtilsWrapper.getSHA1(toInputStream("Hello, World"))
+                fileUtilsWrapper.getSHA1("Hello, World".byteInputStream())
         )
 
         assertEquals(
                 "8b971da6347bd126872ea2f4f8d394e70c74073a",
-                fileUtilsWrapper.getSHA1(toInputStream("apps-android-commons"))
+                fileUtilsWrapper.getSHA1("apps-android-commons".byteInputStream())
         )
 
         assertEquals(
                 "e9d30f5a3a82792b9d79c258366bd53207ceaeb3",
-                fileUtilsWrapper.getSHA1(toInputStream("domdomegg was here"))
+                fileUtilsWrapper.getSHA1("domdomegg was here".byteInputStream())
         )
 
         assertEquals(
                 "96e733a3e59261c0621ba99be5bd10bb21abe53e",
-                fileUtilsWrapper.getSHA1(toInputStream("iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAQAAAC1HAwCAAAAC0lEQVR42mNk+A8AAQUBAScY42YAAAAASUVORK5CYII="))
+                fileUtilsWrapper.getSHA1("iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAQAAAC1HAwCAAAAC0lEQVR42mNk+A8AAQUBAScY42YAAAAASUVORK5CYII=".byteInputStream())
         )
     }
-
-    private fun writeToFile(file: File, s: String) {
-        val buf = BufferedOutputStream(FileOutputStream(file))
-        buf.write(s.toByteArray())
-        buf.close()
-    }
-
-    private fun getString(file: File): String {
-        val bytes = ByteArray(file.length().toInt())
-        val buf = BufferedInputStream(FileInputStream(file))
-        buf.read(bytes, 0, bytes.size)
-        buf.close()
-        return String(bytes)
-    }
-
-    private fun toInputStream(str: String) : InputStream {
-        return ByteArrayInputStream(str.toByteArray(Charsets.UTF_8))
-    }
 }