@Test
    void testNoProblems() {
        ToolchainsBuildingException e = new ToolchainsBuildingException(Collections.emptyList());
        assertEquals("0 problems were encountered while building the effective toolchains" + LS, e.getMessage());
    }

    @Test
    void testOneProblem() {
        ProblemCollector problemCollector = ProblemCollectorFactory.newInstance(null);

    /**
     * Validate the specified settings.
     *
     * @param settings The settings to validate, must not be {@code null}.
     * @param problems The container used to collect problems that were encountered, must not be {@code null}.
     */
    void validate(Settings settings, SettingsProblemCollector problems);

    /**
     * Validate the specified settings.
     *

    /**
     * Gets the problems that were encountered during the settings building. Note that only problems of severity
     * {@link BuilderProblem.Severity#WARNING} and below are reported here. Problems with a higher severity level cause
     * the settings builder to fail with a {@link SettingsBuilderException}.
     *
     * @return the problems that were encountered during the settings building, can be empty but never {@code null}

    /**
     * Gets the problems that were encountered during the settings building. Note that only problems of severity
     * {@link BuilderProblem.Severity#WARNING} and below are reported here. Problems with a higher severity level cause
     * the settings builder to fail with a {@link ToolchainsBuilderException}.
     *
     * @return the problems that were encountered during the settings building, can be empty but never {@code null}

     *
     * @return The decrypted proxy, can be empty but never {@code null}.
     */
    List<Proxy> getProxies();

    /**
     * Gets the problems that were encountered during the settings decryption.
     *
     * @return The problems that were encountered during the decryption, can be empty but never {@code null}.
     */
    List<SettingsProblem> getProblems();

     * @param request The model building request that holds further settings, must not be {@code null}.
     * @param problems The container used to collect problems that were encountered, must not be {@code null}.
     */
    void mergeDuplicates(Model model, ModelBuildingRequest request, ModelProblemCollector problems);

    /**

    /**
     * Gets the problems that were encountered during the settings building. Note that only problems of severity
     * {@link SettingsProblem.Severity#WARNING} and below are reported here. Problems with a higher severity level cause
     * the settings builder to fail with a {@link SettingsBuildingException}.
     *
     * @return The problems that were encountered during the settings building, can be empty but never {@code null}.

 * specific language governing permissions and limitations
 * under the License.
 */
package org.apache.maven.model.building;

/**
 * Collects problems that are encountered during model building. The primary purpose of this component is to account for
 * the fact that the problem reporter has/should not have information about the calling context and hence cannot provide

     *         {@link ProjectBuilderException}.
     */
    @Nonnull
    Optional<Project> getProject();

    /**
     * Gets the problems that were encountered during the project building.
     *
     * @return the problems that were encountered during the project building, can be empty but never {@code null}
     */
    @Nonnull
    Collection<BuilderProblem> getProblems();

    /**

     * @param request The model building request that holds further settings, must not be {@code null}.
     * @param problems The container used to collect problems that were encountered, must not be {@code null}.
     */
    void expandPluginConfiguration(Model model, ModelBuildingRequest request, ModelProblemCollector problems);