@VisibleForTesting
    static Optional<String> findEntryClass(File jarFile) throws IOException {
        return findFirstManifestAttribute(
                jarFile,
                PackagedProgram.MANIFEST_ATTRIBUTE_ASSEMBLER_CLASS,
                PackagedProgram.MANIFEST_ATTRIBUTE_MAIN_CLASS);
    }
@Test
    void testFindEntryClassNoEntry() throws IOException {
        File jarFile = createJarFileWithManifest(ImmutableMap.of());

        Optional<String> entry = JarManifestParser.findEntryClass(jarFile);

        assertThat(entry).isNotPresent();
    }