Fix unit test deadlock

packages/dom/tests/config.rs

@@ -1,11 +1,17 @@
-use std::sync::{Arc, LazyLock, Mutex};
+use std::sync::{Arc, LazyLock, Mutex, MutexGuard};
 
 use testing_library_dom::{configure, get_config, ConfigFnOrPartial, PartialConfig};
 
+static CONFIG_LOCK: Mutex<()> = Mutex::new(());
 static ORIGINAL_CONFIG: LazyLock<Arc<Mutex<PartialConfig>>> =
     LazyLock::new(|| Arc::new(Mutex::new(PartialConfig::default())));
 
-fn before_each() {
+fn before_each() -> MutexGuard<'static, ()> {
+    // Ensure only one test modifies the config at the same time.
+    let lock = CONFIG_LOCK
+        .lock()
+        .expect("Config mutex should be acquired.");
+
     configure(ConfigFnOrPartial::Fn(Box::new(|existing_config| {
         // Grab the existing configuration so we can restore it at the end of the test.
         let mut original_config = ORIGINAL_CONFIG
@@ -16,39 +22,43 @@ fn before_each() {
         // Don't change the existing config.
         PartialConfig::default()
     })));
+
+    lock
 }
 
-fn after_each() {
+fn after_each(lock: MutexGuard<'_, ()>) {
     let original_config = ORIGINAL_CONFIG
         .lock()
         .expect("Original config mutex should be acquired.");
 
     configure(ConfigFnOrPartial::Partial((*original_config).clone()));
+
+    drop(lock);
 }
 
 #[test]
 fn get_config_returns_existing_configuration() {
-    before_each();
+    let lock = before_each();
 
     let config = get_config();
     assert_eq!("data-testid", config.test_id_attribute);
 
-    after_each();
+    after_each(lock);
 }
 
 #[test]
 fn configure_merges_a_delta_rather_than_replacing_the_whole_config() {
-    before_each();
+    let lock = before_each();
 
     let config = get_config();
     assert_eq!("data-testid", config.test_id_attribute);
 
-    after_each();
+    after_each(lock);
 }
 
 #[test]
 fn configure_overrides_existing_values() {
-    before_each();
+    let lock = before_each();
 
     configure(ConfigFnOrPartial::Partial(
         PartialConfig::default().test_id_attribute("new-id".into()),
@@ -57,12 +67,12 @@ fn configure_overrides_existing_values() {
     let config = get_config();
     assert_eq!("new-id", config.test_id_attribute);
 
-    after_each();
+    after_each(lock);
 }
 
 #[test]
 fn configure_passes_existing_config_out_to_config_function() {
-    before_each();
+    let lock = before_each();
 
     // Create a new config key based on the value of an existing one.
     configure(ConfigFnOrPartial::Fn(Box::new(|existing_config| {
@@ -74,5 +84,5 @@ fn configure_passes_existing_config_out_to_config_function() {
     let config = get_config();
     assert_eq!("data-testid-derived", config.test_id_attribute);
 
-    after_each();
+    after_each(lock);
 }