Declare Maven dependency as test runtime only

Question

What is the best way to declare a Maven dependency as only being used for the test runtime (but not test compilation) class path?

Specifically, I want slf4j-api (a logging facade) as a typical, compile-scope dependency, but I want slf4j-simple (the barebones implementation suitable for unit tests) only on the test runtime class path (it's not needed for test compilation). I've been doing this:

<dependency>
  <groupId>org.slf4j</groupId>
  <artifactId>slf4j-api</artifactId>
</dependency>
<dependency>
  <groupId>org.slf4j</groupId>
  <artifactId>slf4j-simple</artifactId>
  <scope>test</scope>
</dependency>

However, the downside of this is that dependency:analyze reports slf4j-simple as unused, presumably because it's not needed for compilation:

[WARNING] Unused declared dependencies found:
[WARNING]    org.slf4j:slf4j-simple:jar:1.7.7:test

I can't use a runtime dependency because I don't want that dependency transitively inherited (e.g. so downstream dependencies can use log4j, etc. instead). I tried runtime with optional=true, but that results in the same warning.

(Note that I could also set ignoreNonCompile for the dependency plugin, but that seems like a very blunt instrument that would hide other potential problems.)

Answer 1

There is no scope that does exactly what you want here; test is the best available option.

A test-runtime scope has been requested before (Re: Need for a test-runtime scope?) and the suggested workaround is exactly the ignoreNonCompile configuration you've already discovered.

dependency:analyze already has some limitations ("some cases are not detected (constants, annotations with source-only retention, links in javadoc)"). You may have to accept that any test-scope dependencies that it warns against are false positives.

(You could split the definition of your tests into a separate module, which would have no slf4j implementation dependencies, then run them in another module. I don't think that would be worth it.)

Answer 2

There is no concept of test-runtime in maven. The only real downside is the dependency analysis identifying these runtime test dependencies as unused. Since they are only test dependencies, however, this is pretty benign and cannot cause issues to other projects transitively dependent on this project.

Answer 3

Since maven-dependency-plugin 2.10 (revision 1649454, Jan 2015), you can also add to the configuration a list of ignoredDependencies, ignoredUnusedDeclaredDependencies and ignoredUsedUndeclaredDependencies.