Set PGAPPNAME for tests

This makes it easier to identify the connections belonging to the test
runs and something else, such as the psql CLI.

Author: arp242

conn_test.go

@@ -132,8 +132,7 @@ func TestPgpass(t *testing.T) {
 	assertPassword("pass_C", map[string]string{"host": "/tmp", "passfile": file, "user": "some_user"})
 
 	// Connection parameter takes precedence
-	os.Setenv("PGPASSFILE", "/tmp")
-	defer os.Unsetenv("PGPASSFILE")
+	t.Setenv("PGPASSFILE", "/tmp")
 	assertPassword("pass_A", map[string]string{"host": "server", "passfile": file, "dbname": "some_db", "user": "some_user"})
 	if warnbuf.String() != "" {
 		t.Errorf("warnbuf not empty: %s", warnbuf)

connector.go

@@ -1043,6 +1043,9 @@ func (cfg Config) string() string {
 				continue
 			}
 		}
+		if k == "application_name" && m[k] == "pqgo" {
+			continue
+		}
 		if k == "host" && len(cfg.multiHost) > 0 {
 			m[k] += "," + strings.Join(cfg.multiHost, ",")
 		}

connector_test.go

@@ -7,7 +7,6 @@ import (
 	"errors"
 	"fmt"
 	"net"
-	"os"
 	"path/filepath"
 	"reflect"
 	"runtime"
@@ -78,8 +77,7 @@ func TestNewConnector(t *testing.T) {
 		useConn(t, db)
 	})
 	t.Run("Environ", func(t *testing.T) {
-		os.Setenv("PGPASSFILE", "/tmp/.pgpass")
-		defer os.Unsetenv("PGPASSFILE")
+		t.Setenv("PGPASSFILE", "/tmp/.pgpass")
 		c, err := NewConnector("")
 		if err != nil {
 			t.Fatal(err)
@@ -102,7 +100,7 @@ func TestNewConnector(t *testing.T) {
 			t.Fatal(err)
 		}
 		want := fmt.Sprintf(
-			`map[client_encoding:UTF8 connect_timeout:20 datestyle:ISO, MDY dbname:pqgo host:localhost max_protocol_version:3.0 min_protocol_version:3.0 port:%d search_path:foo sslmode:disable sslsni:yes user:pqgo]`,
+			`map[application_name:pqgo client_encoding:UTF8 connect_timeout:20 datestyle:ISO, MDY dbname:pqgo host:localhost max_protocol_version:3.0 min_protocol_version:3.0 port:%d search_path:foo sslmode:disable sslsni:yes user:pqgo]`,
 			cfg.Port)
 		if have := fmt.Sprintf("%v", c.cfg.tomap()); have != want {
 			t.Errorf("\nhave: %s\nwant: %s", have, want)
@@ -229,6 +227,7 @@ func TestRuntimeParameters(t *testing.T) {
 		{"fallback_application_name=bar", "application_name", "bar", "", false},
 	}
 
+	pqtest.Unsetenv(t, "PGAPPNAME")
 	for _, tt := range tests {
 		t.Run("", func(t *testing.T) {
 			if tt.skipPgbouncer {
@@ -905,11 +904,7 @@ func TestService(t *testing.T) {
 		[svc5]
 	`), h, ".pg_service.conf")
 
-	// pgbouncer sets PGPORT; not really used to just unset.
-	// TODO: might want to add pqtest.Clearenv() or the like.
-	t.Setenv("PGPORT", "")
-	os.Unsetenv("PGPORT")
-
+	pqtest.Unsetenv(t, "PGPORT")
 	for _, tt := range tests {
 		t.Run("", func(t *testing.T) {
 			for k, v := range tt.env {

internal/pqtest/pqtest.go

@@ -52,6 +52,13 @@ func InvalidCertificate(err error) bool {
 	return false
 }
 
+// Unsetenv unsets the environment variable and uses Cleanup to restore the
+// value after the test.
+//
+// Because Setenv affects the whole process, it cannot be used in parallel tests
+// or tests with parallel ancestors.
+func Unsetenv(t *testing.T, k string) { t.Setenv(k, ""); os.Unsetenv(k) }
+
 // Ptr gets a pointer to any value.
 //
 // TODO(go1.26): replace with new(..) once pq requires Go 1.26.
@@ -73,6 +80,7 @@ func DSN(conninfo string) string {
 		defaultTo("PGUSER", "pqgo")
 		defaultTo("PGSSLMODE", "disable")
 		defaultTo("PGCONNECT_TIMEOUT", "20")
+		os.Setenv("PGAPPNAME", "pqgo")
 	})
 
 	if ForceBinaryParameters() &&