Add run_server helper

spec/std/http/server/server_spec.cr

@@ -107,6 +107,32 @@ private def run_server(server)
   end
 end
 
+# Helper method which runs *server*
+# 1. Spawns `server.listen` in a new fiber.
+# 2. Waits until `server.listening?`.
+# 3. Yields to the given block.
+# 4. Ensures the server is closed.
+# 5. After returning from the block, it waits for the server to gracefully
+#    shut down before continuing execution in the current fiber.
+private def run_server(server)
+  server_done = Channel(Nil).new
+
+  spawn do
+    server.listen
+  ensure
+    server_done.send nil
+  end
+
+  begin
+    wait_for { server.listening? }
+
+    yield server_done
+  ensure
+    server.close unless server.closed?
+    server_done.receive
+  end
+end
+
 module HTTP
   class Server
     describe Response do
@@ -269,10 +295,14 @@ module HTTP
       address = server.bind_unused_port
       address.port.should_not eq(0)
 
+      server.close
+
       server = Server.new { |ctx| }
       port = server.bind_tcp(0).port
       port.should_not eq(0)
 
+    ensure
+      server.close if server
       ensure_no_ports_leaking
     end
 
@@ -395,6 +425,8 @@ module HTTP
       server.bind tcp_server
 
       server.addresses.should eq addresses
+    ensure
+      server.try &.close
       ensure_no_ports_leaking
     end
 
@@ -599,18 +631,13 @@ module HTTP
             server.bind socket1
             socket2 = server.bind_unix path2
 
-            spawn server.listen
-            wait_for { server.listening? }
-
-            unix_request(path1).should eq "Test Server (#{path1})"
-            unix_request(path2).should eq "Test Server (#{path2})"
-
-            server.close
+            run_server(server) do
+              unix_request(path1).should eq "Test Server (#{path1})"
+              unix_request(path2).should eq "Test Server (#{path2})"
+            end
 
             File.exists?(path1).should be_false
             File.exists?(path2).should be_false
-
-            ensure_no_ports_leaking
           ensure
             File.delete(path1) if File.exists?(path1)
             File.delete(path2) if File.exists?(path2)