Move ContentSettingsFragment.isValidPath to helpers and add unit test for it.

app/src/main/java/org/schabi/newpipe/settings/ContentSettingsFragment.java

@@ -26,6 +26,7 @@ import org.schabi.newpipe.extractor.NewPipe;
 import org.schabi.newpipe.extractor.localization.ContentCountry;
 import org.schabi.newpipe.extractor.localization.Localization;
 import org.schabi.newpipe.util.FilePickerActivityHelper;
+import org.schabi.newpipe.util.FilePathUtils;
 import org.schabi.newpipe.util.ZipHelper;
 
 import java.io.File;
@@ -67,7 +68,7 @@ public class ContentSettingsFragment extends BasePreferenceFragment {
                     .putExtra(FilePickerActivityHelper.EXTRA_MODE,
                             FilePickerActivityHelper.MODE_FILE);
             final String path = defaultPreferences.getString(importExportDataPathKey, "");
-            if (isValidPath(path)) {
+            if (FilePathUtils.isValidDirectoryPath(path)) {
                 i.putExtra(FilePickerActivityHelper.EXTRA_START_PATH, path);
             }
             startActivityForResult(i, REQUEST_IMPORT_PATH);
@@ -82,7 +83,7 @@ public class ContentSettingsFragment extends BasePreferenceFragment {
                     .putExtra(FilePickerActivityHelper.EXTRA_MODE,
                             FilePickerActivityHelper.MODE_DIR);
             final String path = defaultPreferences.getString(importExportDataPathKey, "");
-            if (isValidPath(path)) {
+            if (FilePathUtils.isValidDirectoryPath(path)) {
                 i.putExtra(FilePickerActivityHelper.EXTRA_START_PATH, path);
             }
             startActivityForResult(i, REQUEST_EXPORT_PATH);
@@ -254,14 +255,6 @@ public class ContentSettingsFragment extends BasePreferenceFragment {
         }
     }
 
-    private boolean isValidPath(final String path) {
-        if (path == null || path.isEmpty()) {
-            return false;
-        }
-        final File file = new File(path);
-        return file.exists() && file.isDirectory();
-    }
-
     private void setImportExportDataPath(final File file) {
         final String directoryPath;
         if (!file.isDirectory()) {

app/src/main/java/org/schabi/newpipe/util/FilePathUtils.java

@@ -0,0 +1,22 @@
+package org.schabi.newpipe.util;
+
+import java.io.File;
+
+public final class FilePathUtils {
+    private FilePathUtils() { }
+
+
+    /**
+     * Check that the path is a valid directory path and it exists.
+     *
+     * @param path full path of directory,
+     * @return is path valid or not
+     */
+    public static boolean isValidDirectoryPath(final String path) {
+        if (path == null || path.isEmpty()) {
+            return false;
+        }
+        final File file = new File(path);
+        return file.exists() && file.isDirectory();
+    }
+}

app/src/test/java/org/schabi/newpipe/util/FilePathHelperTest.java

@@ -0,0 +1,32 @@
+package org.schabi.newpipe.util;
+
+import org.junit.Test;
+
+import java.io.File;
+import java.io.IOException;
+import java.nio.file.Files;
+
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+
+public class FilePathHelperTest {
+    @Test
+    public void testIsValidDirectoryPath() throws IOException {
+        // path that exists
+        final File dir1 = Files.createTempDirectory("dir1").toFile();
+        assertTrue(FilePathUtils.isValidDirectoryPath(dir1.getAbsolutePath()));
+
+        // a directory in above path that exists
+        final File subDir = Files.createDirectory(dir1.toPath().resolve("subdir")).toFile();
+        assertTrue(FilePathUtils.isValidDirectoryPath(subDir.getAbsolutePath()));
+
+        // a directory in above path that doesn't exist
+        assertFalse(FilePathUtils.isValidDirectoryPath(dir1.toPath().resolve("not-exists-subdir").
+                toFile().getAbsolutePath()));
+
+        // file is not a valid direcotry path
+        final File tempFile = Files.createFile(dir1.toPath().resolve("simple_file")).toFile();
+        assertFalse(FilePathUtils.isValidDirectoryPath(tempFile.getAbsolutePath()));
+    }
+
+}