diff --git a/LoginTest/app/build.gradle b/LoginTest/app/build.gradle
index 05b2def..1e2e884 100644
--- a/LoginTest/app/build.gradle
+++ b/LoginTest/app/build.gradle
@@ -23,6 +23,7 @@ dependencies {
     compile fileTree(dir: 'libs', include: ['*.jar'])
     testCompile 'junit:junit:4.12'
     compile 'com.android.support:appcompat-v7:23.3.0'
-    testCompile "org.mockito:mockito-core:1.+"
+    testCompile 'org.mockito:mockito-core:1.+'
     testCompile 'org.hamcrest:hamcrest-library:1.3'
+    testCompile 'org.robolectric:robolectric:3.0'
 }
diff --git a/LoginTest/app/src/main/java/piotrek/logintest/CredentialsStorage.java b/LoginTest/app/src/main/java/piotrek/logintest/CredentialsStorage.java
new file mode 100644
index 0000000..85a04c1
--- /dev/null
+++ b/LoginTest/app/src/main/java/piotrek/logintest/CredentialsStorage.java
@@ -0,0 +1,26 @@
+package piotrek.logintest;
+
+import android.content.SharedPreferences;
+
+/**
+ * Created by Admin on 2016-04-27.
+ */
+public class CredentialsStorage implements ICredentialsStorage {
+    private final SharedPreferences preferences;
+
+    public CredentialsStorage(SharedPreferences preferences) {
+
+        this.preferences = preferences;
+    }
+
+    @Override
+    public void storeUsername(String username) {
+        preferences
+                .edit()
+                .putString("user", username)
+                .apply();
+
+        // apply - asynchroniczny
+        // commit - synchroniczny
+    }
+}
diff --git a/LoginTest/app/src/test/java/piotrek/logintest/ICredentialsStorageTest.java b/LoginTest/app/src/test/java/piotrek/logintest/ICredentialsStorageTest.java
new file mode 100644
index 0000000..32d0f5f
--- /dev/null
+++ b/LoginTest/app/src/test/java/piotrek/logintest/ICredentialsStorageTest.java
@@ -0,0 +1,36 @@
+package piotrek.logintest;
+
+import android.content.SharedPreferences;
+import android.preference.PreferenceManager;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.robolectric.RobolectricGradleTestRunner;
+import org.robolectric.RuntimeEnvironment;
+import org.robolectric.annotation.Config;
+import org.robolectric.shadows.ShadowPreferenceManager;
+
+import static org.junit.Assert.*;
+
+/**
+ * Created by Admin on 2016-04-27.
+ */
+@RunWith(RobolectricGradleTestRunner.class)
+@Config(constants = BuildConfig.class, sdk = 21)
+public class ICredentialsStorageTest {
+
+    @Test
+    public void should_save_in_shared_preferences() throws Exception {
+        // prepare
+        SharedPreferences preferences = PreferenceManager.getDefaultSharedPreferences(RuntimeEnvironment.application);
+
+        ICredentialsStorage credentialsStorage = new CredentialsStorage(preferences);
+
+        // run
+        credentialsStorage.storeUsername("username");
+        // assert
+
+        String current = preferences.getString("user", null);
+        assertEquals("username", current);
+    }
+}
\ No newline at end of file
diff --git a/LoginTest/app/src/test/java/piotrek/logintest/LoginManagerTests.java b/LoginTest/app/src/test/java/piotrek/logintest/LoginManagerTests.java
index 385275e..71ff0ef 100644
--- a/LoginTest/app/src/test/java/piotrek/logintest/LoginManagerTests.java
+++ b/LoginTest/app/src/test/java/piotrek/logintest/LoginManagerTests.java
@@ -87,6 +87,6 @@ public void setUp() throws Exception {
         when(api.login(anyString(), anyString()))
                 .thenReturn("OK");
 
-        sut = new LoginManager(credentialsStorage, api, view);
+        sut = new LoginManager(credentialsStorage, api);
     }
 }