Add tests for FilePicker public methods (#3948)

Author: neslihanturan

app/src/test/kotlin/fr/free/nrw/commons/filepicker/FilePickerTest.kt

@@ -0,0 +1,57 @@
+package fr.free.nrw.commons.filepicker
+
+import android.app.Activity
+import android.app.Application
+import android.content.SharedPreferences
+import androidx.preference.PreferenceManager
+import com.nhaarman.mockitokotlin2.verify
+import com.nhaarman.mockitokotlin2.verifyNoMoreInteractions
+import fr.free.nrw.commons.filepicker.Constants.RequestCodes
+import fr.free.nrw.commons.filepicker.FilePicker.handleActivityResult
+import junit.framework.Assert.assertEquals
+import org.junit.Before
+import org.junit.Test
+import org.mockito.*
+import org.mockito.Mockito.`when`
+import org.mockito.Mockito.mock
+
+class FilePickerTest {
+    @Mock
+    internal lateinit var activity: Activity
+    @Mock
+    internal lateinit var sharedPref: SharedPreferences
+    @Mock
+    var sharedPreferencesEditor: SharedPreferences.Editor? = null
+    @Mock
+    var unit: Unit? = null
+
+    @Captor
+    var requestCodeCaptor: ArgumentCaptor<Integer>? = null
+
+    @Before
+    fun setup() {
+        MockitoAnnotations.initMocks(this)
+    }
+
+    @Test
+    fun testOpenGalleryRequestCode() {
+        `when`(PreferenceManager.getDefaultSharedPreferences(activity)).thenReturn(sharedPref)
+        `when`(sharedPref.edit()).thenReturn(sharedPreferencesEditor)
+        `when`(sharedPref.edit().putInt("type", 0)).thenReturn(sharedPreferencesEditor)
+        FilePicker.openGallery(activity, 0)
+        verify(activity).startActivityForResult(ArgumentMatchers.anyObject(), requestCodeCaptor?.capture()?.toInt()!!)
+        assertEquals(requestCodeCaptor?.value, RequestCodes.PICK_PICTURE_FROM_GALLERY)
+    }
+
+    @Test
+    fun testOpenCameraForImageCode() {
+        `when`(PreferenceManager.getDefaultSharedPreferences(activity)).thenReturn(sharedPref)
+        `when`(sharedPref.edit()).thenReturn(sharedPreferencesEditor)
+        `when`(sharedPref.edit().putInt("type", 0)).thenReturn(sharedPreferencesEditor)
+        val mockApplication = mock(Application::class.java)
+        `when`(activity.applicationContext).thenReturn(mockApplication)
+        FilePicker.openCameraForImage(activity, 0)
+        verify(activity).startActivityForResult(ArgumentMatchers.anyObject(), requestCodeCaptor?.capture()?.toInt()!!)
+        assertEquals(requestCodeCaptor?.value, RequestCodes.TAKE_PICTURE)
+    }
+}