public async void NoKeys_NewKeyCreated()
        {
            _repositoryMock
            .Setup(x => x.LoadKeysAsync())
            .Returns(Task.FromResult(Enumerable.Empty <SerializedKey>()));
            var serializedNewKey = new SerializedKey {
                KeyId = NewKeyId
            };

            _serializerMock.Setup(x => x.Serialize(It.IsAny <RsaKey>())).Returns(serializedNewKey);

            var result = await _service.GetCurrentKeyAsync();

            _repositoryMock.Verify(
                x => x.StoreKeyAsync(It.Is <SerializedKey>(k => k.KeyId == NewKeyId)), Times.Once);
        }