@Testcontainers
class FileOwnerTest {

    @Container
    static GenericContainer<?> container = new GenericContainer<>("alpine:latest")
        .withCommand("sleep", "infinity");

    @Test
    void testFileOwnership() throws Exception {
        // Create file with specific ownership
        container.copyFileToContainer(
            Transferable.of("hello world".getBytes())
                .withOwner("myuser:mygroup"),  // sets uid:gid
            "/tmp/test.txt"
        );

        // Or copy from local filesystem with ownership
        container.copyFileToContainer(
            MountableFile.forHostPath("/local/path/config.yml")
                .withOwner("1001:1001"),  // numeric uid:gid
            "/app/config.yml"
        );

        // For Dockerfile COPY --chown behavior, build the image with:
        // COPY --chown=myuser:mygroup file.txt /app/
        // and use Testcontainers with that image
    }
}

container.execInContainer("chown", "-R", "1001:1001", "/app/config.yml");