### Question:
MicroconfigRunner { public void build(String env, List<String> groups, List<String> services) { buildProperties(env, groups, services).save(toFiles()); } MicroconfigRunner(File rootDir, File destinationDir); Properties buildProperties(String env, List<String> groups, List<String> services); void build(String env, List<String> groups, List<String> services); PropertySerializer<File> toFiles();  }### Answer:
@Test void testBuild() { File root = classpathFile("repo"); new MicroconfigRunner(root, destinationDir).build("var", emptyList(), emptyList()); File resultFile = new File(destinationDir, "var/service.properties"); assertTrue(resultFile.exists()); assertEquals("c=3", readFully(resultFile)); }