assertEquals("test-group", project.getGroupId(), "groupId proto-inheritance failed.");
        assertEquals("real-artifact", project.getArtifactId(), "artifactId is masked.");
        assertEquals("1000", project.getVersion(), "version proto-inheritance failed.");

        // draw the NPE.
        project.getId();
    }

    @Test
    void testEmptyConstructor() {
        MavenProject project = new MavenProject();

                + (artifact.getClassifier() == null || artifact.getClassifier().isEmpty()
                        ? ""
                        : ":" + artifact.getClassifier())
                + ":" + artifact.getVersion();
    }

    private String id(Artifact artifact) {
        return artifact.key();
    }

            column = e.getColumnNumber();
        }

        ModelProblem problem = new DefaultModelProblem(
                req.getMessage(),
                req.getSeverity(),
                req.getVersion(),
                source,
                line,
                column,
                modelId,
                req.getException());

        add(problem);
    }

     */
    Severity getSeverity();

    /**
     * Gets the applicable maven version/validation level of this problem
     * @return The version, never {@code null}.
     */
    Version getVersion();

                Plugin existing = plugins.get(key);
                if (existing != null) {
                    if (version == null) {
                        version = existing.getVersion();
                    }
                    execs.addAll(existing.getExecutions());
                    deps.addAll(existing.getDependencies());
                }

        path.append(artifact.getArtifactId()).append('/');

        path.append(artifact.getBaseVersion()).append('/');

        path.append(artifact.getArtifactId()).append('-').append(artifact.getVersion());

        if (!artifact.getClassifier().isEmpty()) {
            path.append('-').append(artifact.getClassifier());
        }

        path.append('.').append(artifact.getExtension());

                Plugin plugin = new Plugin();
                plugin.setGroupId(extension.getGroupId());
                plugin.setArtifactId(extension.getArtifactId());
                plugin.setVersion(extension.getVersion());
                XmlNode configuration = extension.getDelegate().getConfiguration();
                if (configuration != null) {
                    plugin.setConfiguration(new Xpp3Dom(configuration));

            List<Artifact> ids = new LinkedList<>();
            ResolutionNode node = this;
            while (node != null) {
                Artifact artifact = node.getArtifact();
                if (artifact.getVersion() == null) {
                    // set the recommended version
                    ArtifactVersion selected = artifact.getSelectedVersion();
                    // MNG-2123: null is a valid response to getSelectedVersion, don't

        // Only select snapshots that are unresolved (eg 1.0-SNAPSHOT, not 1.0-20050607.123456)
        if (artifact.isSnapshot() && artifact.getBaseVersion().equals(artifact.getVersion())) {
            try {
                String version = resolveVersion(artifact, request);
                artifact.updateVersion(version, request.getLocalRepository());

        if (effectiveScope == null) {
            return null;
        }

        VersionRange versionRange = VersionRange.createFromVersionSpec(dependency.getVersion());

        Artifact dependencyArtifact = factory.createDependencyArtifact(
                dependency.getGroupId(),
                dependency.getArtifactId(),
                versionRange,