## Subtests and Sub-benchmarks

### Organizing Related Tests

```go
func TestUser(t *testing.T) {
    // Setup shared by all subtests
    db := setupTestDB(t)

    t.Run("Create", func(t *testing.T) {
        user := &User{Name: "Alice"}
        err := db.CreateUser(user)
        if err != nil {
            t.Fatalf("CreateUser failed: %v", err)
        }
        if user.ID == "" {
            t.Error("expected user ID to be set")
        }
    })

    t.Run("Get", func(t *testing.T) {
        user, err := db.GetUser("alice-id")
        if err != nil {
            t.Fatalf("GetUser failed: %v", err)
        }
        if user.Name != "Alice" {
            t.Errorf("got name %q; want %q", user.Name, "Alice")
        }
    })

    t.Run("Update", func(t *testing.T) {
        // ...
    })

    t.Run("Delete", func(t *testing.T) {
        // ...
    })
}
```

### Parallel Subtests

```go
func TestParallel(t *testing.T) {
    tests := []struct {
        name  string
        input string
    }{
        {"case1", "input1"},
        {"case2", "input2"},
        {"case3", "input3"},
    }

    for _, tt := range tests {
        tt := tt // Capture range variable
        t.Run(tt.name, func(t *testing.T) {
            t.Parallel() // Run subtests in parallel
            result := Process(tt.input)
            // assertions...
            _ = result
        })
    }
}
```