Added test for file opening in TextEditorActivity

app/build.gradle

@@ -59,6 +59,12 @@ android {
         sourceCompatibility JavaVersion.VERSION_1_8
         targetCompatibility JavaVersion.VERSION_1_8
     }
+
+    testOptions {
+        unitTests {
+            includeAndroidResources = true
+        }
+    }
 }
 
 dependencies {
@@ -72,6 +78,10 @@ dependencies {
     implementation 'com.android.support:palette-v7:26.1.0'
     implementation 'com.android.support:cardview-v7:26.1.0'
 
+    //For tests
+    androidTestImplementation 'junit:junit:4.12'//tests the app logic
+    testImplementation "org.robolectric:robolectric:3.6.1"//tests android interaction
+
     //Detect memory leaks
     debugImplementation 'com.squareup.leakcanary:leakcanary-android:1.5.3'
     releaseImplementation 'com.squareup.leakcanary:leakcanary-android-no-op:1.5.3'

app/src/test/java/com/amaze/filemanager/activities/TextEditorActivityTest.java

@@ -0,0 +1,89 @@
+package com.amaze.filemanager.activities;
+
+import android.content.Context;
+import android.content.Intent;
+import android.net.Uri;
+import android.os.Environment;
+import android.widget.TextView;
+
+import com.amaze.filemanager.R;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.robolectric.Robolectric;
+import org.robolectric.RobolectricTestRunner;
+import org.robolectric.RuntimeEnvironment;
+import org.robolectric.android.controller.ActivityController;
+import org.robolectric.shadows.ShadowEnvironment;
+
+import java.io.File;
+import java.io.IOException;
+import java.io.PrintWriter;
+
+import static org.hamcrest.Matchers.is;
+import static org.junit.Assert.assertThat;
+import static org.junit.Assert.fail;
+
+@RunWith(RobolectricTestRunner.class)
+public class TextEditorActivityTest {
+
+    private final String fileContents = "fsdfsdfs";
+    private TextView text;
+
+    @Test
+    public void testOpenFileUri() {
+        File file = simulateFile();
+
+        Intent intent = new Intent(Intent.ACTION_VIEW);
+        intent.setData(Uri.fromFile(file));
+        generateActivity(intent);
+
+        assertThat(text.getText().toString(), is(fileContents + "\n"));
+    }
+
+    @Test
+    public void testOpenContentUri() {
+        File file = simulateFile();
+
+        Intent intent = new Intent(Intent.ACTION_VIEW);
+        intent.setData(getFileContentUri(RuntimeEnvironment.application, file));
+        generateActivity(intent);
+
+        assertThat(text.getText().toString(), is(fileContents + "\n"));
+    }
+
+    private void generateActivity(Intent intent) {
+        ActivityController<TextEditorActivity> controller = Robolectric.buildActivity(TextEditorActivity.class, intent)
+                .create().start().visible();
+
+        TextEditorActivity activity = controller.get();
+        text = activity.findViewById(R.id.fname);
+    }
+
+    private File simulateFile() {
+        ShadowEnvironment.setExternalStorageState(Environment.MEDIA_MOUNTED);
+        File file = new File("text.txt");
+
+        try {
+            file.createNewFile();
+
+            if(!file.canWrite()) file.setWritable(true);
+            assertThat(file.canWrite(), is(true));
+
+            PrintWriter out = new PrintWriter(file);
+            out.write(fileContents);
+            out.flush();
+            out.close();
+        } catch (IOException e) {
+            fail(e.getMessage());
+        }
+
+        return file;
+    }
+
+    private Uri getFileContentUri(Context context, File file) {
+        fail("Cannot create content URI");
+        return null;
+    }
+
+}

text.txt

@@ -0,0 +1 @@
+fsdfsdfs