@Test
    public void resolve_FileKey() throws Exception {
        Path path = getPath("secret.key");
        String input = Paths.get("").toUri().relativize(path.toUri()).getPath();
        String output = resolve("${readFile:" + input + "}");
        assertThat(output, equalTo(FILE.lookup(input)));
        assertThat(output, startsWith("-----BEGIN RSA PRIVATE KEY-----"));
    }
Ensures that prefixes in the secret ID which are not covered by the CasC protocol substitutors (e.g. base64:, file:)
are left untouched and not removed.
plugin/src/test/java/io/jenkins/plugins/casc/SecretSourceResolverTest.java