feat(test): diagnose failed effect assertions

hemx-test/src/lib.rs

@@ -492,10 +492,28 @@ impl EffectInspector {
         })
     }
 
-    /// Assert that a generated target receives an HTML update containing text.
+    /// Check that a generated target receives an HTML update containing text.
     /// req: test/001 req: dx/006
     pub fn updates_html_containing(&self, target: impl GeneratedTarget, needle: &str) -> bool {
+        self.has_html_update_containing(target.__hemx_resource_id(), needle)
+    }
+
+    /// Assert that a generated target receives an HTML update containing text.
+    ///
+    /// Unlike wrapping [`Self::updates_html_containing`] in `assert!`, failures include the
+    /// expected resource and payload fragment together with every actual effect operation.
+    /// req: test/001 req: test/018 req: dx/006
+    #[track_caller]
+    pub fn assert_updates_html_containing(&self, target: impl GeneratedTarget, needle: &str) {
         let resource = target.__hemx_resource_id();
+        assert!(
+            self.has_html_update_containing(resource, needle),
+            "expected an HTML update for {resource:?} containing {needle:?}; actual effects: {:#?}",
+            self.batch.ops
+        );
+    }
+
+    fn has_html_update_containing(&self, resource: ResourceId, needle: &str) -> bool {
         self.batch.ops.iter().any(|op| {
             matches!(
                 op,