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

Beyond t.Error and t.Fatal, Go's testing package offers several methods that eliminate boilerplate and make test intent clearer. Knowing these marks a candidate as familiar with Go testing idioms.

// 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
        })
    }
}

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