pw.println("key3 = val3");
        pw.println("");

        MavenProperties props = new MavenProperties();
        props.load(new StringReader(sw.toString()));
        props.save(System.err);
        System.err.println("=====");

        props.put("key2", props.get("key2"));
        props.put("key3", "foo");
        props.save(System.err);
        System.err.println("=====");
    }

    @Test

        Properties props = new Properties();
        props.put("key", "user_value");
        ToolchainModel toolchain = new ToolchainModel();
        toolchain.setType("TYPE");
        toolchain.setProvides(props);
        PersistedToolchains userResult = new PersistedToolchains();
        userResult.setToolchains(Collections.singletonList(toolchain));

        props = new Properties();

                if (error != null) {
                    props.setProperty(key + ERROR_KEY_SUFFIX, error);
                } else {
                    props.remove(key + ERROR_KEY_SUFFIX);
                }

                getLogger().debug("Writing resolution-state to: " + touchfile);
                channel.truncate(0);

        return p;
    }

    private Properties newProperties(String osName, String osVersion, String osArch) {
        Properties props = new Properties();
        props.setProperty("os.name", osName);
        props.setProperty("os.version", osVersion);
        props.setProperty("os.arch", osArch);
        return props;
    }

    @Test
    void testVersionStringComparison() throws Exception {

        Map<String, String> props = new LinkedHashMap<>();
        props.put("javax.version", "3.1.0");
        props.put("mockito.version", "1.10.19");
        props.put("hamcret.version", "2.1");
        props.put("lombok.version", "1.18.6");
        props.put("junit.version", "4.12");
        Model model = Model.newBuilder(true).properties(props).build();
        String xml = toXml(model);

    @Test
    public void testRecursiveExpressionCycleNPE() throws Exception {
        Map<String, String> props = new HashMap<>();
        props.put("aa", "${bb}");
        props.put("bb", "${aa}");
        DefaultModelBuildingRequest request = new DefaultModelBuildingRequest();

        Model model = Model.newBuilder().properties(props).build();

        SimpleProblemCollector collector = new SimpleProblemCollector();

        assertActivation(true, profile, newContext(null, newProperties("other", "")));
    }

    @Test
    void testWithValue_UserPropertyDominantOverSystemProperty() throws Exception {
        Profile profile = newProfile("prop", "value");

        Properties props1 = newProperties("prop", "value");
        Properties props2 = newProperties("prop", "other");

            version = artifact.getVersionRange().toString();
        }

        Map<String, String> props = null;
        if (org.apache.maven.artifact.Artifact.SCOPE_SYSTEM.equals(artifact.getScope())) {
            String localPath = (artifact.getFile() != null) ? artifact.getFile().getPath() : "";
            props = Collections.singletonMap(MavenArtifactProperties.LOCAL_PATH, localPath);
        }

            Artifact artifact = result.getArtifact();
            Map<String, String> props = new HashMap<>(artifact.getProperties());
            props.put(ArtifactProperties.DOWNLOAD_URL, downloadUrl);
            result.setArtifact(artifact.setProperties(props));
        }
    }

        Properties props = cliRequest.getUserProperties();
        if (cliRequest.getRootDirectory() != null) {
            props = new Properties();
            props.putAll(cliRequest.getUserProperties());
            props.put("session.rootDirectory", cliRequest.getRootDirectory().toString());
        }
        settingsRequest.setUserProperties(props);