code: @Test public void jarIsOnlyRepackagedOnce() throws Exception {
    this.testJarFile.addClass("a/b/C.class",ClassWithMainMethod.class);
    File file=this.testJarFile.getFile();
    Repackager repackager=new Repackager(file);
    repackager.repackage(NO_LIBRARIES);
    repackager.repackage(NO_LIBRARIES);
    Manifest actualManifest=getManifest(file);
    assertThat(actualManifest.getMainAttributes().getValue("Main-Class"),equalTo("org.springframework.boot.loader.JarLauncher"));
    assertThat(actualManifest.getMainAttributes().getValue("Start-Class"),equalTo("a.b.C"));
    assertThat(hasLauncherClasses(file),equalTo(true));
  }
  