test: Improve the server status test to not race and randomly fail (#7304)

Co-authored-by: Alex Kremer <akremer@ripple.com>

src/test/jtx/WSClient_test.cpp

@@ -13,8 +13,9 @@ class WSClient_test : public beast::unit_test::Suite
 {
 public:
     void
-    run() override
+    testSmoke()
     {
+        testcase("smoke");
         using namespace jtx;
         Env env(*this);
         auto wsc = makeWSClient(env.app().config());
@@ -28,6 +29,47 @@ public:
         auto jv = wsc->getMsg(std::chrono::seconds(1));
         pass();
     }
+
+    void
+    testGracefulDisconnect()
+    {
+        testcase("graceful disconnect");
+        using namespace jtx;
+        using namespace std::chrono;
+
+        Env env(*this);
+        auto wsc = makeWSClient(env.app().config());
+
+        // Put real traffic on the connection before closing it.
+        json::Value stream;
+        stream["streams"] = json::ValueType::Array;
+        stream["streams"].append("ledger");
+        auto const sub = wsc->invoke("subscribe", stream);
+        BEAST_EXPECT(sub.isMember("result") || sub.isMember("status"));
+
+        // disconnect() performs a graceful WebSocket closing handshake and
+        // blocks until the server acknowledges. On loopback that completes in
+        // well under its internal 1s timeout; only a broken async_close/ack
+        // coordination would fall through to the force-close path at ~1s. A
+        // generous bound keeps this from flaking under load while still
+        // catching that regression.
+        auto const start = steady_clock::now();
+        wsc->disconnect();
+        auto const elapsed = duration_cast<milliseconds>(steady_clock::now() - start);
+        BEAST_EXPECT(elapsed < milliseconds{750});
+
+        // disconnect() must be idempotent: a second call (and the subsequent
+        // destructor) must not hang, double-close, or crash.
+        wsc->disconnect();
+        pass();
+    }
+
+    void
+    run() override
+    {
+        testSmoke();
+        testGracefulDisconnect();
+    }
 };
 
 BEAST_DEFINE_TESTSUITE(WSClient, jtx, xrpl);