如何在 Golang 中测试 map 的等价性？

这就是我要做的（未经测试的代码）：

func eq(a, b map[string]int) bool {
        if len(a) != len(b) {
                return false
        }

        for k, v := range a {
                if w, ok := b[k]; !ok || v != w {
                        return false
                }
        }

        return true
}

---

请改用 cmp (https://github.com/google/go-cmp)：

if !cmp.Equal(src, expectedSearchSource) {
    t.Errorf("Wrong object received, got=%s", cmp.Diff(expectedSearchSource, src))
}

https://i.stack.imgur.com/MPJg9.png

当您预期输出中的地图“顺序”不是您的函数返回的内容时，它仍然会失败。但是，cmp 仍然能够指出不一致的地方。

作为参考，我发现了这条推文：

https://twitter.com/francesc/status/885630175668346880?lang=en

“在测试中使用 reflect.DeepEqual 通常是个坏主意，这就是我们开源 http://github.com/google/go-cmp 的原因” - Joe Tsai

---

免责声明：与 map[string]int 无关，但与在 Go 中测试地图的等价性有关，这是问题的标题

如果您有一个指针类型的映射（如 map[*string]int），那么您 do not want to use reflect.DeepEqual 因为它将返回 false。

最后，如果键是包含未导出指针的类型，例如 time.Time，则在这样的映射 can also return false 上反射.DeepEqual。

---

使用 github.com/google/go-cmp/cmp 的“Diff”方法：

代码：

// Let got be the hypothetical value obtained from some logic under test
// and want be the expected golden data.
got, want := MakeGatewayInfo()

if diff := cmp.Diff(want, got); diff != "" {
    t.Errorf("MakeGatewayInfo() mismatch (-want +got):\n%s", diff)
}

输出：

MakeGatewayInfo() mismatch (-want +got):
  cmp_test.Gateway{
    SSID:      "CoffeeShopWiFi",
-   IPAddress: s"192.168.0.2",
+   IPAddress: s"192.168.0.1",
    NetMask:   net.IPMask{0xff, 0xff, 0x00, 0x00},
    Clients: []cmp_test.Client{
        ... // 2 identical elements
        {Hostname: "macchiato", IPAddress: s"192.168.0.153", LastSeen: s"2009-11-10 23:39:43 +0000 UTC"},
        {Hostname: "espresso", IPAddress: s"192.168.0.121"},
        {
            Hostname:  "latte",
-           IPAddress: s"192.168.0.221",
+           IPAddress: s"192.168.0.219",
            LastSeen:  s"2009-11-10 23:00:23 +0000 UTC",
        },
+       {
+           Hostname:  "americano",
+           IPAddress: s"192.168.0.188",
+           LastSeen:  s"2009-11-10 23:03:05 +0000 UTC",
+       },
    },
  }

---

最简单的方法：

    assert.InDeltaMapValues(t, got, want, 0.0, "Word count wrong. Got %v, want %v", got, want)

例子：

import (
    "github.com/stretchr/testify/assert"
    "testing"
)

func TestCountWords(t *testing.T) {
    got := CountWords("hola hola que tal")

    want := map[string]int{
        "hola": 2,
        "que": 1,
        "tal": 1,
    }

    assert.InDeltaMapValues(t, got, want, 0.0, "Word count wrong. Got %v, want %v", got, want)
}

---