Add test for FileUtils

app/src/test/java/fr/free/nrw/commons/FileUtilsTest.java

@@ -0,0 +1,40 @@
+package fr.free.nrw.commons;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+import java.io.BufferedInputStream;
+import java.io.BufferedOutputStream;
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.FileOutputStream;
+import java.io.IOException;
+
+import fr.free.nrw.commons.upload.FileUtils;
+
+import static org.hamcrest.CoreMatchers.is;
+
+public class FileUtilsTest {
+    @Test public void copiedFileIsIdenticalToSource() throws IOException {
+        File source = File.createTempFile("temp", "");
+        File dest = File.createTempFile("temp", "");
+        writeToFile(source, "Hello, World");
+        FileUtils.copy(new FileInputStream(source), new FileOutputStream(dest));
+        Assert.assertThat(getString(dest), is(getString(source)));
+    }
+
+    private static void writeToFile(File file, String s) throws IOException {
+        BufferedOutputStream buf = new BufferedOutputStream(new FileOutputStream(file));
+        buf.write(s.getBytes());
+        buf.close();
+    }
+
+    private static String getString(File file) throws IOException {
+        int size = (int) file.length();
+        byte[] bytes = new byte[size];
+        BufferedInputStream buf = new BufferedInputStream(new FileInputStream(file));
+        buf.read(bytes, 0, bytes.length);
+        buf.close();
+        return new String(bytes);
+    }
+}