return getProjectSelectors(pa -> !pa.optional && pa.active);
    }

    /**
     * @return Optional active project selectors, never {@code null}.
     */
    public Set<String> getOptionalActiveProjectSelectors() {
        return getProjectSelectors(pa -> pa.optional && pa.active);
    }

    /**
     * @return Required inactive project selectors, never {@code null}.
     */

        Set<String> requiredSelectors = projectActivation.getRequiredActiveProjectSelectors();
        Set<String> optionalSelectors = projectActivation.getOptionalActiveProjectSelectors();
        if (!requiredSelectors.isEmpty() || !optionalSelectors.isEmpty()) {
            Set<MavenProject> selectedProjects = new HashSet<>(requiredSelectors.size() + optionalSelectors.size());

        assertThat(activation.getRequiredActiveProjectSelectors(), containsInAnyOrder("test1", "test2"));
        assertThat(activation.getOptionalActiveProjectSelectors(), containsInAnyOrder("test3", "test4"));

        activation = new ProjectActivation();
        performProjectActivation(

        final ProjectActivation projectActivation = request.getProjectActivation();
        final Set<String> allOptionalSelectors = new HashSet<>();
        allOptionalSelectors.addAll(projectActivation.getOptionalActiveProjectSelectors());
        allOptionalSelectors.addAll(projectActivation.getRequiredActiveProjectSelectors());
        // We intentionally ignore the results of this method.