test: Add polymorphic-body integration coverage for oneOf

Replace stub /anyOf and /allOf fixture routes with a real /shapes
endpoint that uses oneOf to discriminate between circle and square
request bodies. Adds an integration test verifying both valid
branches return 200 and that bodies matching zero branches return
400 application/problem+json with the oneOf keyword in the body.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: thced

src/test/java/com/retailsvc/http/OpenApiServerIT.java

@@ -402,4 +402,92 @@ void getPathParams_shouldReturnInternalErrorOnMissingHandler() {
       }
     }
   }
+
+  @Nested
+  class Shapes {
+
+    String path = "/shapes";
+
+    @Test
+    void postShape_validCircleReturns200() {
+      try (var server =
+              newServer(Map.of("post-shape", new com.retailsvc.http.start.PolymorphicHandler()));
+          var client = httpClient()) {
+        var body = "{\"kind\":\"circle\",\"radius\":2.5}";
+        var request = newRequest(server, path, "POST", ofString(body));
+
+        var response = client.send(request, BodyHandlers.ofString());
+
+        assertThat(response.statusCode()).isEqualTo(200);
+        assertThat(response.body()).contains("\"ok\":true");
+      } catch (IOException e) {
+        fail(e);
+      } catch (InterruptedException e) {
+        Thread.currentThread().interrupt();
+        fail(e);
+      }
+    }
+
+    @Test
+    void postShape_validSquareReturns200() {
+      try (var server =
+              newServer(Map.of("post-shape", new com.retailsvc.http.start.PolymorphicHandler()));
+          var client = httpClient()) {
+        var body = "{\"kind\":\"square\",\"side\":3}";
+        var request = newRequest(server, path, "POST", ofString(body));
+
+        var response = client.send(request, BodyHandlers.ofString());
+
+        assertThat(response.statusCode()).isEqualTo(200);
+      } catch (IOException e) {
+        fail(e);
+      } catch (InterruptedException e) {
+        Thread.currentThread().interrupt();
+        fail(e);
+      }
+    }
+
+    @Test
+    void postShape_unknownKindReturns400() {
+      // matches zero branches: "kind" is neither "circle" nor "square".
+      try (var server =
+              newServer(Map.of("post-shape", new com.retailsvc.http.start.PolymorphicHandler()));
+          var client = httpClient()) {
+        var body = "{\"kind\":\"triangle\",\"side\":3}";
+        var request = newRequest(server, path, "POST", ofString(body));
+
+        var response = client.send(request, BodyHandlers.ofString());
+
+        assertThat(response.statusCode()).isEqualTo(400);
+        assertThat(response.headers().firstValue("Content-Type").orElse(""))
+            .contains("application/problem+json");
+        assertThat(response.body()).contains("oneOf");
+      } catch (IOException e) {
+        fail(e);
+      } catch (InterruptedException e) {
+        Thread.currentThread().interrupt();
+        fail(e);
+      }
+    }
+
+    @Test
+    void postShape_missingDiscriminatorReturns400() {
+      // omitting "kind" makes both branches fail "required".
+      try (var server =
+              newServer(Map.of("post-shape", new com.retailsvc.http.start.PolymorphicHandler()));
+          var client = httpClient()) {
+        var body = "{\"radius\":2.5}";
+        var request = newRequest(server, path, "POST", ofString(body));
+
+        var response = client.send(request, BodyHandlers.ofString());
+
+        assertThat(response.statusCode()).isEqualTo(400);
+      } catch (IOException e) {
+        fail(e);
+      } catch (InterruptedException e) {
+        Thread.currentThread().interrupt();
+        fail(e);
+      }
+    }
+  }
 }

src/test/java/com/retailsvc/http/start/PolymorphicHandler.java

@@ -0,0 +1,19 @@
+package com.retailsvc.http.start;
+
+import com.sun.net.httpserver.HttpExchange;
+import com.sun.net.httpserver.HttpHandler;
+import java.io.IOException;
+import java.nio.charset.StandardCharsets;
+
+public class PolymorphicHandler implements HttpHandler {
+
+  @Override
+  public void handle(HttpExchange exchange) throws IOException {
+    byte[] body = "{\"ok\":true}".getBytes(StandardCharsets.UTF_8);
+    exchange.getResponseHeaders().add("Content-Type", "application/json");
+    exchange.sendResponseHeaders(200, body.length);
+    try (var out = exchange.getResponseBody()) {
+      out.write(body);
+    }
+  }
+}

src/test/resources/openapi.json

@@ -170,14 +170,37 @@
         }
       }
     },
-    "/anyOf": {
+    "/shapes": {
       "post": {
-
-      }
-    },
-    "/allOf": {
-      "post": {
-
+        "operationId": "post-shape",
+        "requestBody": {
+          "required": true,
+          "content": {
+            "application/json": {
+              "schema": {
+                "oneOf": [
+                  {
+                    "type": "object",
+                    "required": ["kind", "radius"],
+                    "properties": {
+                      "kind": { "type": "string", "enum": ["circle"] },
+                      "radius": { "type": "number" }
+                    }
+                  },
+                  {
+                    "type": "object",
+                    "required": ["kind", "side"],
+                    "properties": {
+                      "kind": { "type": "string", "enum": ["square"] },
+                      "side": { "type": "number" }
+                    }
+                  }
+                ]
+              }
+            }
+          }
+        },
+        "responses": { "200": { "description": "OK" } }
       }
     }
   },

src/test/resources/openapi.yaml

@@ -109,11 +109,34 @@ paths:
         "200":
           description: OK
 
-  /anyOf:
-    post: {}
-
-  /allOf:
-    post: {}
+  /shapes:
+    post:
+      operationId: post-shape
+      requestBody:
+        required: true
+        content:
+          application/json:
+            schema:
+              oneOf:
+                - type: object
+                  required: [kind, radius]
+                  properties:
+                    kind:
+                      type: string
+                      enum: [circle]
+                    radius:
+                      type: number
+                - type: object
+                  required: [kind, side]
+                  properties:
+                    kind:
+                      type: string
+                      enum: [square]
+                    side:
+                      type: number
+      responses:
+        "200":
+          description: OK
 
 components:
   parameters: