What key aspect of dbt enhances code reusability?

The key aspect of dbt that enhances code reusability is its macro functionalities. Macros in dbt are essentially reusable pieces of code that can be defined once and used multiple times across different models. This allows analytics engineers to write complex SQL code once, encapsulate it in a macro, and then invoke it wherever needed throughout their project. This not only saves time and effort but also maintains consistency and reduces the likelihood of errors since the same logic can be reused instead of rewriting it multiple times in different places.

The other choices do not contribute to code reusability in the same way. Data visualization tools are mainly concerned with presenting data rather than reusing code logic. Automated testing features are important for ensuring the quality and accuracy of the data transformation processes, but they do not enhance reusability. Real-time data streaming focuses on how data is ingested and processed rather than how the code can be reused within dbt projects. Thus, the macro functionalities stand out as the most relevant feature for increasing code reusability in dbt.