Add unit tests and repair doc-teststopic/tests

2 files changed, 41 insertions, 1 deletions

diff --git a/libsyslog/src/lib.rs b/libsyslog/src/lib.rs
index 7c253ae..c154ec5 100644
--- a/libsyslog/src/lib.rs
+++ b/libsyslog/src/lib.rs
@@ -13,7 +13,8 @@
 //! Typical use: (A.k.a. recommended snippet to copy'n'paste to the start of
 //! `main()` of your daemon.)
 //! ```
-//! # fn main() -> Result<()> {
+//! # use log::error;
+//! # fn main() -> Result<(), log::SetLoggerError> {
 //! libsyslog::Syslog::builder()
 //!     .module_level(std::module_path!(), log::LevelFilter::Info)
 //!     .level(log::LevelFilter::Off)
@@ -21,6 +22,7 @@
 //!     .init()?;
 //!
 //! error!("Hello libsyslog. I've failed you.");
+//! # Ok(())
 //! # }
 //! ```
 //!
@@ -57,6 +59,9 @@ mod facility;
 mod logopt;
 mod syslog;
 
+#[cfg(test)]
+mod tests;
+
 #[cfg(feature = "bitflags")]
 pub use logopt::*;
 
diff --git a/libsyslog/src/tests.rs b/libsyslog/src/tests.rs
new file mode 100644
index 0000000..f3eeca7
--- /dev/null
+++ b/libsyslog/src/tests.rs
@@ -0,0 +1,35 @@
+use crate::Syslog;
+
+#[test]
+fn call_init_twice() {
+    // 0. First test that a first call to initialize works.
+    if Syslog::builder().build().init().is_err() {
+        panic!("First request to initialize Syslog failed.");
+    }
+
+    // 1. Then assure that another attempt fails, as there can only be one logger.
+    //
+    //    Reminder to self: Since this init() already returns a Result, there is no real need to
+    //    deal with implementing a separate check with `std::sync::Once`. The log crate practically
+    //    covers our ass here.
+    if Syslog::builder().build().init().is_ok() {
+        panic!("Second request to initialize Syslog unexpectedly succeeded.");
+    }
+}
+
+// NOTE It would be neat to have higher test coverage, including some of the actual logging, but
+//      the question is how to obtain that in a meaningful way. Stubbing out `libsyslog-sys` would
+//      make the tests mostly pointless, right? Targetting the host's `/dev/log` through `syslog()`
+//      practically leads to nothing but unverifiable side-effects. Running with a custom syslogd
+//      look-a-like, in a chroot or by other conceivable means, would require priviledges not
+//      suitable for unit testing.
+//
+//      On a more practical level, multiple tests can not run in threads of the same test runner
+//      due to the singleton nature of Syslog, plus the fact that the foreign functions openlog()
+//      and closelog() should really only be called once per process.
+//
+//      There is https://github.com/rust-lang/rust/issues/47506 which points out this probem, but
+//      the closest to a solution mentioned is a recommendation to use the `rusty-fork` crate. A
+//      crate that seems to need a bit more love than anyone appears to be able to give it. By the
+//      look of things, https://github.com/AltSysrq/rusty-fork/pull/10 is approaching three years
+//      of waiting in a believed-to-be-mergable state.