Add test support for loading files from the resources directory

Author: Amejia481

components/concept/engine/src/test/java/mozilla/components/concept/engine/manifest/WebAppManifestParserTest.kt

@@ -7,6 +7,7 @@ package mozilla.components.concept.engine.manifest
 import android.graphics.Color
 import android.graphics.Color.rgb
 import androidx.test.ext.junit.runners.AndroidJUnit4
+import mozilla.components.support.test.file.loadResourceAsString
 import org.json.JSONObject
 import org.junit.Assert.assertEquals
 import org.junit.Assert.assertFalse
@@ -580,12 +581,7 @@ class WebAppManifestParserTest {
     }
 
     private fun loadManifestAsString(fileName: String): String =
-        javaClass.getResourceAsStream("/manifests/$fileName")!!
-            .bufferedReader().use {
-                it.readText()
-            }.also {
-                assertNotNull(it)
-            }
+        loadResourceAsString("/manifests/$fileName")
 
     private fun loadManifest(fileName: String): JSONObject =
         JSONObject(loadManifestAsString(fileName))

components/support/test/src/main/java/mozilla/components/support/test/file/Resources.kt

@@ -0,0 +1,19 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+package mozilla.components.support.test.file
+
+import org.junit.Assert
+
+/**
+ * Loads a file from the resources folder and return its content as a string object.
+ * @param path The path where the file is located
+ */
+fun Any.loadResourceAsString(path: String): String {
+    return javaClass.getResourceAsStream(path)!!.bufferedReader().use {
+        it.readText()
+    }.also {
+        Assert.assertNotNull(it)
+    }
+}

components/support/test/src/test/java/mozilla/components/support/test/file/ResourcesTest.kt

@@ -0,0 +1,20 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+package mozilla.components.support.test.robolectric.mozilla.components.support.test.file
+
+import androidx.test.ext.junit.runners.AndroidJUnit4
+import mozilla.components.support.test.file.loadResourceAsString
+import org.junit.Assert.assertEquals
+import org.junit.Test
+import org.junit.runner.RunWith
+
+@RunWith(AndroidJUnit4::class)
+class ResourcesTest {
+
+    @Test
+    fun getProvidedAppContext() {
+        assertEquals("42", loadResourceAsString("/example_file.txt"))
+    }
+}