From the Azure SQL Database container to Azure SQL Database: same code, local to cloud

Build and test against the local container, then deploy the same application code to Azure SQL Database in the cloud. Only the connection string changes. Nothing else.

This works because the local container is the Azure SQL Database engine, not the SQL Server image. SELECT SERVERPROPERTY('EngineEdition') returns 5 and SERVERPROPERTY('Edition') returns 'SQL Azure', the same as the cloud. So the SQL surface your code depends on is the same in both places.