    @Test
    public void classpath_file() throws IOException {

        Path file = tempDir.newFile("classpath.txt").toPath();

        Files.write(file, Arrays.asList("", "", "")); // empty lines are ignored
        systemProperties.setProperty(RetrolambdaApi.CLASSPATH_FILE, file.toString());
        assertThat("zero values", config().getClasspath(), is(empty()));

        Files.write(file, Arrays.asList("one.jar"));
        systemProperties.setProperty(RetrolambdaApi.CLASSPATH_FILE, file.toString());
        assertThat("one value", config().getClasspath(), is(Arrays.asList(Paths.get("one.jar"))));

        Files.write(file, Arrays.asList("one.jar", "two.jar"));
        systemProperties.setProperty(RetrolambdaApi.CLASSPATH_FILE, file.toString());
        assertThat("multiple values", config().getClasspath(), is(Arrays.asList(Paths.get("one.jar"), Paths.get("two.jar"))));
    }