testutils: enable backtrace capture by default (RUST_LIB_BACKTRACE=1) in tests

So backtraces are shown without requiring the environment variable.

Author: glehmann

lib/testutils/src/lib.rs

@@ -87,6 +87,13 @@ pub mod test_backend;
 fn init_color_eyre() {
     use color_eyre::config::HookBuilder;
 
+    // Enable backtrace capture by default in tests
+    if std::env::var("RUST_BACKTRACE").is_err() {
+        unsafe {
+            std::env::set_var("RUST_BACKTRACE", "1");
+        }
+    }
+
     drop(
         HookBuilder::default()
             .capture_span_trace_by_default(false)