diff --git a/internal/ircserver/server_test.go b/internal/ircserver/server_test.go
index f30b826..1cc4316 100644
--- a/internal/ircserver/server_test.go
+++ b/internal/ircserver/server_test.go
@@ -137,20 +137,6 @@ func newTestEnvWithResolver(
 
 	brk := broker.New()
 
-	var listenConfig net.ListenConfig
-
-	listener, err := listenConfig.Listen(t.Context(), "tcp", "127.0.0.1:0")
-	if err != nil {
-		t.Fatalf("listen: %v", err)
-	}
-
-	addr := listener.Addr().String()
-
-	err = listener.Close()
-	if err != nil {
-		t.Fatalf("close listener: %v", err)
-	}
-
 	log := slog.New(slog.NewTextHandler(
 		os.Stderr,
 		&slog.HandlerOptions{Level: slog.LevelError}, //nolint:exhaustruct
@@ -160,7 +146,9 @@ func newTestEnvWithResolver(
 		log, cfg, database, brk, interval, deadline, resolve,
 	)
 
-	err = srv.Start(addr)
+	// Port 0 makes the system pick a free port. dial reads it
+	// back from the server's listener.
+	err = srv.Start("127.0.0.1:0")
 	if err != nil {
 		t.Fatalf("start irc server: %v", err)
 	}
diff --git a/internal/server/server_test.go b/internal/server/server_test.go
index 874231e..f4d7cde 100644
--- a/internal/server/server_test.go
+++ b/internal/server/server_test.go
@@ -8,7 +8,6 @@ import (
 	"fmt"
 	"net"
 	"net/http"
-	"strconv"
 	"strings"
 	"testing"
 	"time"
@@ -45,10 +44,9 @@ const (
 // for a long poll the HTTP server is serving to finish, and
 // that the poll gets its response.
 func TestStopWaitsForRequestInProgress(t *testing.T) {
-	port := freePort(t)
-	addr := net.JoinHostPort("127.0.0.1", strconv.Itoa(port))
+	var srv *server.Server
 
-	app, brk, database := startApp(t, port)
+	app, brk, database := startApp(t, fx.Populate(&srv))
 
 	sessionID, _, token, err := database.CreateSession(
 		t.Context(), "poller", "poller", "", "",
@@ -57,9 +55,20 @@ func TestStopWaitsForRequestInProgress(t *testing.T) {
 		t.Fatalf("create session: %v", err)
 	}
 
-	waitUntil(t, "the HTTP server to listen", func() bool {
-		return canConnect(t, addr)
-	})
+	// The test cannot read the port the system gave the app, so
+	// it serves the same HTTP server on a listener of its own.
+	var listenConfig net.ListenConfig
+
+	listener, err := listenConfig.Listen(
+		t.Context(), "tcp", "127.0.0.1:0",
+	)
+	if err != nil {
+		t.Fatalf("listen: %v", err)
+	}
+
+	go srv.ServeUntilShutdown(listener)
+
+	addr := listener.Addr().String()
 
 	statuses := make(chan int, 1)
 
@@ -145,7 +154,7 @@ func TestStartFailsWhenHTTPPortIsTaken(t *testing.T) {
 func TestServeFailureStopsApp(t *testing.T) {
 	var srv *server.Server
 
-	app, _, _ := startApp(t, freePort(t), fx.Populate(&srv))
+	app, _, _ := startApp(t, fx.Populate(&srv))
 
 	shutdowns := app.Wait()
 
@@ -168,7 +177,7 @@ func TestServeFailureStopsApp(t *testing.T) {
 func TestServeAfterStopDoesNotStopApp(t *testing.T) {
 	var srv *server.Server
 
-	app, _, _ := startApp(t, freePort(t), fx.Populate(&srv))
+	app, _, _ := startApp(t, fx.Populate(&srv))
 
 	shutdowns := app.Wait()
 
@@ -186,16 +195,15 @@ func TestServeAfterStopDoesNotStopApp(t *testing.T) {
 	}
 }
 
-// startApp starts the app newApp builds, with the HTTP server
-// listening on port.
+// startApp starts the app newApp builds, with the HTTP port
+// set to 0, so the system gives the server a free port.
 func startApp(
 	t *testing.T,
-	port int,
 	options ...fx.Option,
 ) (*fxtest.App, *broker.Broker, *db.Database) {
 	t.Helper()
 
-	app, brk, database := newApp(t, port, options...)
+	app, brk, database := newApp(t, 0, options...)
 
 	app.RequireStart()
 
@@ -254,21 +262,6 @@ func newApp(
 	return app, brk, database
 }
 
-// freePort returns a TCP port that nothing was listening on a
-// moment ago.
-func freePort(t *testing.T) int {
-	t.Helper()
-
-	listener := closedListener(t)
-
-	tcpAddr, ok := listener.Addr().(*net.TCPAddr)
-	if !ok {
-		t.Fatalf("listener address %v is not TCP", listener.Addr())
-	}
-
-	return tcpAddr.Port
-}
-
 // closedListener returns a TCP listener that has already been
 // closed, so that accepting a connection on it fails.
 func closedListener(t *testing.T) net.Listener {
@@ -291,22 +284,6 @@ func closedListener(t *testing.T) net.Listener {
 	return listener
 }
 
-// canConnect reports whether addr accepts a TCP connection.
-func canConnect(t *testing.T, addr string) bool {
-	t.Helper()
-
-	var dialer net.Dialer
-
-	conn, err := dialer.DialContext(t.Context(), "tcp", addr)
-	if err != nil {
-		return false
-	}
-
-	_ = conn.Close()
-
-	return true
-}
-
 // waitUntil calls done every checkStep until it returns true,
 // and fails the test if it does not within testTimeout.
 func waitUntil(t *testing.T, what string, done func() bool) {