Go: What are table-driven tests in Go?

1// Simple example
2func TestAdd(t *testing.T) {
3    tests := []struct {
4        name     string
5        a, b     int
6        expected int
7    }{
8        {"positive", 2, 3, 5},
9        {"zero", 0, 0, 0},
10        {"negative", -1, -2, -3},
11        {"mixed", -1, 1, 0},
12    }
13
14    for _, tt := range tests {
15        t.Run(tt.name, func(t *testing.T) {
16            result := Add(tt.a, tt.b)
17            if result != tt.expected {
18                t.Errorf("Add(%d, %d) = %d, want %d", tt.a, tt.b, result, tt.expected)
19            }
20        })
21    }
22}
23
24// With errors
25func TestDivide(t *testing.T) {
26    tests := []struct {
27        name    string
28        a, b    float64
29        want    float64
30        wantErr bool
31    }{
32        {"normal", 10, 2, 5, false},
33        {"by zero", 10, 0, 0, true},
34        {"negative", -10, 2, -5, false},
35    }
36
37    for _, tt := range tests {
38        t.Run(tt.name, func(t *testing.T) {
39            got, err := Divide(tt.a, tt.b)
40            if (err != nil) != tt.wantErr {
41                t.Errorf("error = %v, wantErr %v", err, tt.wantErr)
42                return
43            }
44            if got != tt.want {
45                t.Errorf("Divide(%f, %f) = %f, want %f", tt.a, tt.b, got, tt.want)
46            }
47        })
48    }
49}
50
51// With setup/teardown
52func TestWithDB(t *testing.T) {
53    tests := []struct {
54        name  string
55        query string
56        want  int
57    }{
58        {"count users", "SELECT COUNT(*) FROM users", 10},
59        {"count orders", "SELECT COUNT(*) FROM orders", 5},
60    }
61
62    for _, tt := range tests {
63        t.Run(tt.name, func(t *testing.T) {
64            db := setupTestDB(t)
65            defer db.Close()
66
67            var count int
68            err := db.QueryRow(tt.query).Scan(&count)
69            if err != nil {
70                t.Fatal(err)
71            }
72            if count != tt.want {
73                t.Errorf("got %d, want %d", count, tt.want)
74            }
75        })
76    }
77}