What testing.T methods do experienced Go engineers use to write cleaner tests?

// t.Helper() — marks current function as a test helper
// Error messages show the caller's line, not the helper's line
func requireNoError(t *testing.T, err error, msg string) {
    t.Helper() // CRITICAL: without this, failure shows helper's line
    if err != nil {
        t.Fatalf("%s: %v", msg, err)
    }
}

// t.Cleanup() — deferred cleanup, runs even if test panics
func TestDBOperation(t *testing.T) {
    db := openTestDB(t)
    t.Cleanup(func() { db.Close() }) // cleaner than defer for table tests

    user := createTestUser(t, db)
    t.Cleanup(func() {
        db.Exec("DELETE FROM users WHERE id = $1", user.ID)
    })
    // test code...
}

// t.Setenv() — sets env var for the test, auto-restores on cleanup
func TestLoadConfig(t *testing.T) {
    t.Setenv("DATABASE_URL", "postgres://test:test@localhost/testdb")
    t.Setenv("JWT_SECRET", "test-secret-at-least-32-chars-long")
    cfg, err := loadConfig()
    requireNoError(t, err, "loadConfig")
    if cfg.Database.URL == "" { t.Error("DATABASE_URL not loaded") }
}

// t.TempDir() — creates a temp directory that's auto-removed
func TestWriteFile(t *testing.T) {
    dir := t.TempDir() // automatically cleaned up after test
    path := filepath.Join(dir, "output.json")
    err := writeJSON(path, map[string]string{"ok": "true"})
    requireNoError(t, err, "writeJSON")
}

// t.Parallel() — run subtests concurrently for faster test suites
func TestConcurrentOperations(t *testing.T) {
    for _, tc := range testCases {
        tc := tc // capture pre-Go 1.22
        t.Run(tc.name, func(t *testing.T) {
            t.Parallel() // this subtest runs concurrently with others
            // ... test body
        })
    }
}