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.)

what is this is required at runtime for main source ? won't it still complain for runtime scoped dependency ? — jmj
In general transitive dependencies need not be declared. For an optional dependency (typically like logging which can use different frameworks) your procedure is right. Maybe you can add a scope test too. — Joop Eggen
It does also complain (wrongly, IMHO) for a runtime dependency, so it seems like scope alone is not the answer here. What I really want is a scope that is the intersection of test and runtime (as far as the class path) and for the dependency plugin to act less dumb about "unused" runtime dependencies. — Trevor Robinson

Joe Joe · Accepted Answer · 2015-01-01T09:59:36

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.)

Declare Maven dependency as test runtime only

4 Answers