test(rmcp): add missing edge case tests from code review

Add tests identified during code review:
- description stripping for primitive types
- composition types (Option<String> with anyOf/oneOf/null)
- cache correctness (Arc::ptr_eq for repeated calls)
- schema_for_input rejecting array types (not just primitives)
- schema_for_output accepting unit type ()

Author: Brandon Bennett

crates/rmcp/src/handler/server/common.rs

@@ -319,6 +319,42 @@ mod tests {
         assert_eq!(schema.get("type"), Some(&serde_json::json!("integer")));
     }
 
+    #[test]
+    fn test_schema_for_output_strips_description_for_primitive() {
+        let schema = schema_for_output::<i32>();
+        assert!(!schema.contains_key("description"));
+    }
+
+    #[test]
+    fn test_schema_for_output_accepts_composition() {
+        let schema = schema_for_output::<Option<String>>();
+        let schema_str = serde_json::to_string(&schema).unwrap();
+        assert!(
+            schema_str.contains("anyOf")
+                || schema_str.contains("oneOf")
+                || schema_str.contains("null"),
+            "Expected composition schema for Option<String>, got: {schema_str}"
+        );
+    }
+
+    #[test]
+    fn test_schema_for_output_caches_result() {
+        let schema1 = schema_for_output::<i32>();
+        let schema2 = schema_for_output::<i32>();
+        assert!(Arc::ptr_eq(&schema1, &schema2));
+    }
+
+    #[test]
+    fn test_schema_for_input_rejects_array() {
+        let result = schema_for_input::<Vec<i32>>();
+        assert!(result.is_err());
+    }
+
+    #[test]
+    fn test_schema_for_output_accepts_unit() {
+        let _schema = schema_for_output::<()>();
+    }
+
     #[test]
     fn test_schema_for_output_accepts_object() {
         let schema = schema_for_output::<TestObject>();

crates/rmcp/tests/test_json_schema_detection.rs

@@ -174,10 +174,7 @@ async fn test_json_string_type_generates_schema() {
     let server = TestServer::new();
     let tools = server.tool_router.list_all();
 
-    let string_tool = tools
-        .iter()
-        .find(|t| t.name == "with-json-string")
-        .unwrap();
+    let string_tool = tools.iter().find(|t| t.name == "with-json-string").unwrap();
     assert!(
         string_tool.output_schema.is_some(),
         "Json<String> return type should generate output schema"

crates/rmcp/tests/test_structured_output.rs

@@ -95,7 +95,10 @@ impl TestServer {
     }
 
     /// Tool that returns a list of calculation results
-    #[tool(name = "calculate-list", description = "Return a list of calculation results")]
+    #[tool(
+        name = "calculate-list",
+        description = "Return a list of calculation results"
+    )]
     pub async fn calculate_list(
         &self,
         params: Parameters<CalculationRequest>,

crates/rmcp/tests/test_tool_builder_methods.rs

@@ -76,8 +76,8 @@ fn test_with_output_schema_primitive() {
 
 #[test]
 fn test_with_output_schema_array() {
-    let tool = Tool::new("test", "Test tool", JsonObject::new())
-        .with_output_schema::<Vec<String>>();
+    let tool =
+        Tool::new("test", "Test tool", JsonObject::new()).with_output_schema::<Vec<String>>();
 
     assert!(tool.output_schema.is_some());
 
@@ -90,8 +90,8 @@ fn test_with_output_schema_array() {
 
 #[test]
 fn test_with_output_schema_option() {
-    let tool = Tool::new("test", "Test tool", JsonObject::new())
-        .with_output_schema::<Option<String>>();
+    let tool =
+        Tool::new("test", "Test tool", JsonObject::new()).with_output_schema::<Option<String>>();
 
     assert!(tool.output_schema.is_some());