Add sample test for WiFiServer

Mostly an example of writing tests for servers

tests/device/test_WiFiServer/test_WiFiServer.ino

@@ -0,0 +1,54 @@
+#include <Arduino.h>
+#include <ESP8266WiFi.h>
+#include <ESP8266mDNS.h>
+#include <WiFiClient.h>
+#include <BSTest.h>
+#include <test_config.h>
+
+
+BS_ENV_DECLARE();
+
+void setup()
+{
+    Serial.begin(115200);
+    WiFi.persistent(false);
+    WiFi.begin(STA_SSID, STA_PASS);
+    while (WiFi.status() != WL_CONNECTED) {
+        delay(500);
+    }
+    MDNS.begin("esp8266-wfs-test");
+    BS_RUN(Serial);
+}
+
+TEST_CASE("Simple echo server", "[WiFiServer]")
+{
+    const uint32_t timeout = 10000;
+    const uint16_t port = 5000;
+    const int maxRequests = 5;
+    const int minRequestLength = 128;
+    WiFiServer server(port);
+    server.begin();
+    auto start = millis();
+    
+    int replyCount = 0;
+    while (millis() - start < timeout) {
+        delay(50);
+        WiFiClient client = server.available();
+        if (!client) {
+            continue;
+        }
+        String request = client.readStringUntil('\n');
+        CHECK(request.length() >= minRequestLength);
+        client.print(request);
+        client.print('\n');
+        if (++replyCount == maxRequests) {
+            break;
+        }
+    }
+    CHECK(replyCount == maxRequests);
+}
+
+void loop()
+{
+}
+