ADR-004 Reduce mapstructmapper tests to a minimum

Status

accepted

Context

Testing is all about showing the functionality of our application. We rely on the fact that the frameworks and libraries we use during development are sufficiently tested. Therefore, we can focus on testing our logic while writing tests, especially unit tests.

Decision

Mappers are only tested if we define explicit mapping logic. This explicit mapping logic is present, for example, when we define default implementations in interfaces or map fields with different names via the @mapping annotation or define an expression for the mapping.

Via the configuration of the mapstructprocessor for the maven-compile-plugin, it is defined that all fields in the target object are considered for mapping.

If a field is not part of the mapping declaration, an error should occur.

Todo

• Add compiler argument at maven-compile-plugin: -Amapstruct.unmappedTargetPolicy=ERROR
• Ignore target properties when mapping if they are not fillable by the source object: @Mapping(target="ignorableProp", ignore=true)

Consequences

There are fewer tests to write, but we rely more on Mapstruct to work correctly. More knowledge about Mapstruct is required, since assumptions are less checked.