public void AssertJsonSerializer() { string connectionString = "AccountEndpoint=https://localtestcosmos.documents.azure.com:443/;AccountKey=425Mcv8CXQqzRNCgFNjIhT424GK99CKJvASowTnq15Vt8LeahXTcN5wt3342vQ==;"; var cosmosClientBuilder = new CosmosClientBuilder(connectionString); var cosmosClient = cosmosClientBuilder.Build(new MockDocumentClient()); Assert.IsInstanceOfType(cosmosClient.ClientOptions.CosmosSerializerWithWrapperOrDefault, typeof(CosmosJsonSerializerWrapper)); Assert.AreEqual(cosmosClient.ClientOptions.CosmosSerializerWithWrapperOrDefault, cosmosClient.ClientOptions.PropertiesSerializer); CosmosSerializer defaultSerializer = cosmosClient.ClientOptions.PropertiesSerializer; CosmosSerializer mockJsonSerializer = new Mock <CosmosSerializer>().Object; cosmosClientBuilder.WithCustomJsonSerializer(mockJsonSerializer); var cosmosClientCustom = cosmosClientBuilder.Build(new MockDocumentClient()); Assert.AreEqual(defaultSerializer, cosmosClientCustom.ClientOptions.PropertiesSerializer); Assert.AreEqual(mockJsonSerializer, cosmosClientCustom.ClientOptions.Serializer); Assert.IsInstanceOfType(cosmosClientCustom.ClientOptions.CosmosSerializerWithWrapperOrDefault, typeof(CosmosJsonSerializerWrapper)); Assert.AreEqual(mockJsonSerializer, ((CosmosJsonSerializerWrapper)cosmosClientCustom.ClientOptions.CosmosSerializerWithWrapperOrDefault).InternalJsonSerializer); }