AuthenticationProvider_test.dart

void main() {
  group('AuthenticationProvider', () {
    //Mock and inject the basic dependencies in the AuthenticationProvider
    FirebaseAuthMock firebaseAuth = FirebaseAuthMock();
    GoogleSignInMock googleSignIn = GoogleSignInMock();

    AuthenticationProvider authenticationProvider = AuthenticationProvider(
        firebaseAuth: firebaseAuth, googleSignIn: googleSignIn);

    //Mock rest of the objects needed to replicate the AuthenticationProvider functions
    final GoogleSignInAccountMock googleSignInAccount =
        GoogleSignInAccountMock();
    final GoogleSignInAuthenticationMock googleSignInAuthentication =
        GoogleSignInAuthenticationMock();
    final FirebaseUserMock firebaseUser = FirebaseUserMock();
    SharedPreferencesMock sharedPreferencesMock = SharedPreferencesMock();
    SharedObjects.prefs = sharedPreferencesMock;

    test('signInWithGoogle returns a Firebase user', () async {
      //mock the method calls
      when(sharedPreferencesMock.getString(any)).thenReturn('uid');
      when(SharedObjects.prefs.setString(any, any)).thenAnswer((_)=>Future.value(true));
      when(googleSignIn.signIn()).thenAnswer(
          (_) => Future<GoogleSignInAccountMock>.value(googleSignInAccount));
      when(googleSignInAccount.authentication).thenAnswer((_) =>
          Future<GoogleSignInAuthenticationMock>.value(
              googleSignInAuthentication));
      when(firebaseAuth.currentUser())
          .thenAnswer((_) => Future<FirebaseUserMock>.value(firebaseUser));

      //call the method and expect the Firebase user as return
      expect(await authenticationProvider.signInWithGoogle(), firebaseUser);
      verify(googleSignIn.signIn()).called(1);
      verify(googleSignInAccount.authentication).called(1);
    });

    test('getCurrentUser returns current user', () async {
      when(firebaseAuth.currentUser())
          .thenAnswer((_) => Future<FirebaseUserMock>.value(firebaseUser));
      expect(await authenticationProvider.getCurrentUser(), firebaseUser);
    });

    test('isLoggedIn return true only when FirebaseAuth has a user', () async {
      when(firebaseAuth.currentUser())
          .thenAnswer((_) => Future<FirebaseUserMock>.value(firebaseUser));
      expect(await authenticationProvider.isLoggedIn(), true);
      when(firebaseAuth.currentUser())
          .thenAnswer((_) => Future<FirebaseUserMock>.value(null));
      expect(await authenticationProvider.isLoggedIn(), false);
    });

    test('signOutUser clears the session', () async {
      when(sharedPreferencesMock.getString(Constants.sessionUsername)).thenReturn('username');
      expect(SharedObjects.prefs.getString(Constants.sessionUsername),'username');

      //mocking all the methods use by signOutUser
      when(firebaseAuth.signOut()).thenAnswer((_)=>Future<void>(null));
      when(googleSignIn.signOut()).thenAnswer((_)=>Future.value(googleSignInAccount));
      when(sharedPreferencesMock.clearSession()).thenAnswer((_){
        when(sharedPreferencesMock.getString(Constants.sessionUsername)).thenReturn(null);
        return;
      });
      authenticationProvider.signOutUser();
      expect(SharedObjects.prefs.getString(Constants.sessionUsername),null);
    });

});
}