why patches.Reset not effective?

[Zjmainstay]

Behaviors:

1. Only one test case can run normally every time.
2. Multiple test cases lead to different random results.

file1: http_request.go

package test

import (
	"fmt"
	"io"
	"net/http"
)

func GetIp(url string) string {
	// 发送GET请求
	response, err := http.Get(url)
	if err != nil {
		fmt.Printf("请求发生错误: %s\n", err)
		return ""
	}
	defer response.Body.Close()

	// 读取响应数据
	body, err := io.ReadAll(response.Body)
	fmt.Println("ioReadAll", string(body), err)
	if err != nil {
		fmt.Printf("读取响应数据发生错误: %s\n", err)
		return ""
	}

	return string(body)
}

file2:http_request_test.go

package test

import (
	"bytes"
	"errors"
	"fmt"
	"io"
	"net/http"
	"reflect"
	"testing"

	"github.com/agiledragon/gomonkey/v2"
)

func TestGetIp(t *testing.T) {
	tests := []struct {
		name            string
		url             string
		mockHttpGetFunc func(url string) (resp *http.Response, err error)
		mockReadAllFunc func(r io.Reader) ([]byte, error)
		expectIp        string
		expectErr       bool
	}{
		{
			name: "正常获取IP信息",
			url:  "http://valid.url",
			mockHttpGetFunc: func(url string) (resp *http.Response, err error) {
				return &http.Response{StatusCode: http.StatusOK, Body: io.NopCloser(bytes.NewBufferString("192.168.0.1"))}, nil
			},
			mockReadAllFunc: func(r io.Reader) ([]byte, error) {
				return []byte("192.168.0.1"), nil
			},
			expectIp: "192.168.0.1",
		},
		{
			name: "http.Get错误",
			url:  "http://invalid.url",
			mockHttpGetFunc: func(url string) (resp *http.Response, err error) {
				return nil, errors.New("http get error")
			},
		},
		{
			name: "io.ReadAll错误",
			url:  "http://valid.url",
			mockHttpGetFunc: func(url string) (resp *http.Response, err error) {
				return &http.Response{StatusCode: http.StatusOK, Body: io.NopCloser(bytes.NewBufferString("192.168.0.2"))}, nil
			},
			mockReadAllFunc: func(r io.Reader) ([]byte, error) {
				return nil, errors.New("read all error")
			},
		},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			patches := gomonkey.NewPatches()
			defer patches.Reset()
			fmt.Println(tt.name, "tt.mockHttpGetFunc is nil:", tt.mockHttpGetFunc == nil)
			fmt.Println(tt.name, "tt.mockReadAllFunc is nil:", tt.mockReadAllFunc == nil)
			patches.ApplyFunc(io.ReadAll, tt.mockReadAllFunc)
			patches.ApplyFunc(http.Get, tt.mockHttpGetFunc)

			ip := GetIp(tt.url)

			if !reflect.DeepEqual(ip, tt.expectIp) {
				t.Errorf("GetIp() = %v, expect %v", ip, tt.expectIp)
			}
		})
	}
}

test command

go test -gcflags=all=-l

result unexpect

正常获取IP信息 tt.mockHttpGetFunc is nil: false
正常获取IP信息 tt.mockReadAllFunc is nil: false
ioReadAll 192.168.0.1 <nil>
http.Get错误 tt.mockHttpGetFunc is nil: false
http.Get错误 tt.mockReadAllFunc is nil: true
请求发生错误: http get error
io.ReadAll错误 tt.mockHttpGetFunc is nil: false
io.ReadAll错误 tt.mockReadAllFunc is nil: false
ioReadAll 192.168.0.1 <nil>
--- FAIL: TestGetIp (0.00s)
    --- FAIL: TestGetIp/io.ReadAll错误 (0.00s)
        http_request_test.go:66: GetIp() = 192.168.0.1, expect 
FAIL
exit status 1
FAIL    godemo/test/http_request        0.005s

--------------------------------------------------------------

正常获取IP信息 tt.mockHttpGetFunc is nil: false
正常获取IP信息 tt.mockReadAllFunc is nil: false
ioReadAll 192.168.0.1 <nil>
http.Get错误 tt.mockHttpGetFunc is nil: false
http.Get错误 tt.mockReadAllFunc is nil: true
ioReadAll 192.168.0.1 <nil>
io.ReadAll错误 tt.mockHttpGetFunc is nil: false
io.ReadAll错误 tt.mockReadAllFunc is nil: false
ioReadAll 192.168.0.1 <nil>
--- FAIL: TestGetIp (0.00s)
    --- FAIL: TestGetIp/http.Get错误 (0.00s)
        http_request_test.go:66: GetIp() = 192.168.0.1, expect 
    --- FAIL: TestGetIp/io.ReadAll错误 (0.00s)
        http_request_test.go:66: GetIp() = 192.168.0.1, expect 
FAIL
exit status 1
FAIL    godemo/test/http_request        0.006s

result expect

正常获取IP信息 tt.mockHttpGetFunc is nil: false
正常获取IP信息 tt.mockReadAllFunc is nil: false
ioReadAll 192.168.0.1 <nil>
http.Get错误 tt.mockHttpGetFunc is nil: false
http.Get错误 tt.mockReadAllFunc is nil: true
请求发生错误: http get error
io.ReadAll错误 tt.mockHttpGetFunc is nil: false
io.ReadAll错误 tt.mockReadAllFunc is nil: false
ioReadAll  read all error
读取响应数据发生错误: read all error
PASS
ok      godemo/test/http_request        0.005s

[xhd2015]

Note that gomonkey is not concurrent safe.
If you need that, can try https://github.com/xhd2015/xgo