MockTail

repository_test.dart

class MockRemoteDataSource extends Mock implements RemoteDateSource{}

void main(){
  test("fetch() should return an instance of student on remoteDataSource's fetch success", () {
    //Arrange
    MockRemoteDateSource mockDS = MockRemoteDateSource();
    Repository repo = Repository(mockDS);
    when(mockDS.fetch()).thenReturn("Mock Result");
    //Act
    final result = repo.fetch();
    //Assert
    expect(result, isInstanceOf<Student>());
  });

  test("fetch() should throw an exception on remoteDataSource's fetch throws any exception", () {
    MockRemoteDateSource mockDS = MockRemoteDateSource();
    Repository repo = Repository(mockDS);
    when(mockDS.fetch()).thenThrow(SocketException("Mock exception"));
    expect(() => repo.fetch(), throwsException);
  });
}