ThemeHelper mockThemeHelper = new ThemeHelper() {
            @Override
            protected Path getJarFile(Artifact artifact) {
                return jarPath;
            }
        };

        Artifact artifact = new Artifact("fess-theme-test", "1.0.0");
        Path result = mockThemeHelper.getJarFile(artifact);
        assertEquals(jarPath, result);
    }

    public void test_getJarFile_notExists() {