in maven-plugin-testing-harness/src/main/java/org/apache/maven/plugin/testing/ArtifactStubFactory.java [348:355]
public Set<Artifact> getClassifiedArtifacts() throws IOException {
Set<Artifact> set = new HashSet<>();
set.add(createArtifact("g", "a", "1.0", Artifact.SCOPE_COMPILE, "jar", "one"));
set.add(createArtifact("g", "b", "1.0", Artifact.SCOPE_COMPILE, "jar", "two"));
set.add(createArtifact("g", "c", "1.0", Artifact.SCOPE_COMPILE, "jar", "three"));
set.add(createArtifact("g", "d", "1.0", Artifact.SCOPE_COMPILE, "jar", "four"));
return set;
}