Give each IRC listener test its own database (closes #129)

Each test environment in internal/ircserver named its shared in-memory
database after the test. A repeat run of a test in the same process
could open the database that an earlier run's server was still
holding, and start on that run's users. The database now gets a random
name, and a new test checks that two environments open at once do not
share one.

The database close and the server stop are now registered as soon as
each is opened, so a setup that fails part-way still closes its
database.

Model: opus-5-5

internal/ircserver/server_test.go

@@ -2,6 +2,7 @@ package ircserver_test
 
 import (
 	"bufio"
+	"crypto/rand"
 	"database/sql"
 	"fmt"
 	"log/slog"
@@ -69,9 +70,11 @@ func newTestEnvWithConfig(
 ) *testEnv {
 	t.Helper()
 
+	// A random name, so that no other test environment, not
+	// even an earlier run of the same test, can share it.
 	dsn := fmt.Sprintf(
 		"file:%s?mode=memory&cache=shared&_journal_mode=WAL",
-		t.Name(),
+		rand.Text(),
 	)
 
 	conn, err := sql.Open("sqlite", dsn)
@@ -79,6 +82,13 @@ func newTestEnvWithConfig(
 		t.Fatalf("open db: %v", err)
 	}
 
+	t.Cleanup(func() {
+		err := conn.Close()
+		if err != nil {
+			t.Logf("close db: %v", err)
+		}
+	})
+
 	conn.SetMaxOpenConns(1)
 
 	_, err = conn.ExecContext(
@@ -123,14 +133,9 @@ func newTestEnvWithConfig(
 		t.Fatalf("start irc server: %v", err)
 	}
 
-	t.Cleanup(func() {
-		srv.Stop()
-
-		err := conn.Close()
-		if err != nil {
-			t.Logf("close db: %v", err)
-		}
-	})
+	// Cleanups run last registered first, so the server stops
+	// before its database is closed.
+	t.Cleanup(srv.Stop)
 
 	return &testEnv{
 		database: database,
@@ -342,6 +347,20 @@ func TestRegistration(t *testing.T) {
 	assertContains(t, lines, " 001 ", "RPL_WELCOME")
 }
 
+// TestEachTestEnvHasItsOwnDatabase checks that a test
+// environment starts on an empty database while another one
+// is still open.
+func TestEachTestEnvHasItsOwnDatabase(t *testing.T) {
+	t.Parallel()
+
+	first := newTestEnv(t)
+	first.dial(t).register("samenick")
+
+	second := newTestEnv(t)
+	lines := second.dial(t).register("samenick")
+	assertContains(t, lines, " 001 ", "RPL_WELCOME")
+}
+
 func TestWelcomeContainsNick(t *testing.T) {
 	t.Parallel()