单测时尽量用Fake Object，你学会了吗？

// $GOROOT/src/database/fakedb_test.go

var fdriver driver.Driver = &fakeDriver{}

func init() {
    Register("test", fdriver)
}

// fakeDriver is a fake database that implements Go's driver.Driver
// interface, just for testing.
//
// It speaks a query language that's semantically similar to but
// syntactically different and simpler than SQL.  The syntax is as
// follows:
//
//  WIPE
//  CREATE|<tablename>|<col>=<type>,<col>=<type>,...
//    where types are: "string", [u]int{8,16,32,64}, "bool"
//  INSERT|<tablename>|col=val,col2=val2,col3=?
//  SELECT|<tablename>|projectcol1,projectcol2|filtercol=?,filtercol2=?
//  SELECT|<tablename>|projectcol1,projectcol2|filtercol=?param1,filtercol2=?param2

// 被测对象 client.go

package main

import (
 "bytes"
 "net/http"
)

// Function that uses the client to make a request and parse the response
func GetResponse(client *http.Client, url string) (string, error) {
 req, err := http.NewRequest("GET", url, nil)
 if err != nil {
  return "", err
 }

 resp, err := client.Do(req)
 if err != nil {
  return "", err
 }
 defer resp.Body.Close()

 buf := new(bytes.Buffer)
 _, err = buf.ReadFrom(resp.Body)
 if err != nil {
  return "", err
 }

 return buf.String(), nil
}

// 测试代码 client_test.go

package main

import (
 "net/http"
 "net/http/httptest"
 "testing"
)

func TestClient(t *testing.T) {
 // Create a new test server with a handler that returns a specific response
 server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
  w.WriteHeader(http.StatusOK)
  w.Write([]byte(`{"message": "Hello, world!"}`))
 }))
 defer server.Close()

 // Create a new client that uses the test server
 client := server.Client()

 // Call the function that uses the client
 message, err := GetResponse(client, server.URL)

 // Check that the response is correct
 expected := `{"message": "Hello, world!"}`
 if message != expected {
  t.Errorf("Expected response %q, but got %q", expected, message)
 }

 // Check that no errors were returned
 if err != nil {
  t.Errorf("Unexpected error: %v", err)
 }
}

// handler.go

package main
  
import (
    "bytes"
    "io"
    "net/http"
)

func AddHelloPrefix(w http.ResponseWriter, r *http.Request) {
    b, err := io.ReadAll(r.Body)
    if err != nil {
        w.WriteHeader(http.StatusBadRequest)
        return
    }
    w.Write(bytes.Join([][]byte{[]byte("hello, "), b}, nil))
    w.WriteHeader(http.StatusOK)
}

// handler_test.go

package main
  
import (
    "net/http"
    "net/http/httptest"
    "strings"
    "testing"
)

func TestHandler(t *testing.T) {
    r := strings.NewReader("world!")
    req, err := http.NewRequest("GET", "/test", r)
    if err != nil {
        t.Fatal(err)
    }

    rr := httptest.NewRecorder()
    handler := http.HandlerFunc(AddHelloPrefix)
    handler.ServeHTTP(rr, req)

    if status := rr.Code; status != http.StatusOK {
        t.Errorf("handler returned wrong status code: got %v want %v",
            status, http.StatusOK)
    }

    expected := "hello, world!"
    if rr.Body.String() != expected {
        t.Errorf("handler returned unexpected body: got %v want %v",
            rr.Body.String(), expected)
    }
}

// db.go 被测目标

package main

// Define the `Database` interface
type Database interface {
    Save(data string) error
    Get(id int) (string, error)
}

// Example functions that use the `Database` interface
func saveData(db Database, data string) error {
    return db.Save(data)
}

func getData(db Database, id int) (string, error) {
    return db.Get(id)
}

// 测试代码

package main

import (
 "testing"

 "github.com/stretchr/testify/assert"
 "github.com/stretchr/testify/mock"
)

// Define a mock struct that implements the `Database` interface
type MockDatabase struct {
 mock.Mock
}

func (m *MockDatabase) Save(data string) error {
 args := m.Called(data)
 return args.Error(0)
}

func (m *MockDatabase) Get(id int) (string, error) {
 args := m.Called(id)
 return args.String(0), args.Error(1)
}

func TestSaveData(t *testing.T) {
 // Create a new mock database
 db := new(MockDatabase)

 // Expect the `Save` method to be called with "test data"
 db.On("Save", "test data").Return(nil)

 // Call the code that uses the database
 err := saveData(db, "test data")

 // Assert that the `Save` method was called with the correct argument
 db.AssertCalled(t, "Save", "test data")

 // Assert that no errors were returned
 assert.NoError(t, err)
}

func TestGetData(t *testing.T) {
 // Create a new mock database
 db := new(MockDatabase)

 // Expect the `Get` method to be called with ID 123 and return "test data"
 db.On("Get", 123).Return("test data", nil)

 // Call the code that uses the database
 data, err := getData(db, 123)

 // Assert that the `Get` method was called with the correct argument
 db.AssertCalled(t, "Get", 123)

 // Assert that the correct data was returned
 assert.Equal(t, "test data", data)

 // Assert that no errors were returned
 assert.NoError(t, err)
}

// redis_test.go

package main

import (
 "context"
 "fmt"
 "testing"

 "github.com/go-redis/redis/v8"
 "github.com/testcontainers/testcontainers-go"
 "github.com/testcontainers/testcontainers-go/wait"
)

func TestRedisClient(t *testing.T) {
 // Create a Redis container with a random port and wait for it to start
 req := testcontainers.ContainerRequest{
  Image:        "redis:latest",
  ExposedPorts: []string{"6379/tcp"},
  WaitingFor:   wait.ForLog("Ready to accept connections"),
 }
 ctx := context.Background()
 redisC, err := testcontainers.GenericContainer(ctx, testcontainers.GenericContainerRequest{
  ContainerRequest: req,
  Started:          true,
 })
 if err != nil {
  t.Fatalf("Failed to start Redis container: %v", err)
 }
 defer redisC.Terminate(ctx)

 // Get the Redis container's host and port
 redisHost, err := redisC.Host(ctx)
 if err != nil {
  t.Fatalf("Failed to get Redis container's host: %v", err)
 }
 redisPort, err := redisC.MappedPort(ctx, "6379/tcp")
 if err != nil {
  t.Fatalf("Failed to get Redis container's port: %v", err)
 }

 // Create a Redis client and perform some operations
 client := redis.NewClient(&redis.Options{
  Addr: fmt.Sprintf("%s:%s", redisHost, redisPort.Port()),
 })
 defer client.Close()

 err = client.Set(ctx, "key", "value", 0).Err()
 if err != nil {
  t.Fatalf("Failed to set key: %v", err)
 }

 val, err := client.Get(ctx, "key").Result()
 if err != nil {
  t.Fatalf("Failed to get key: %v", err)
 }

 if val != "value" {
  t.Errorf("Expected value %q, but got %q", "value", val)
 }
}

$go test
2023/04/15 16:18:20 github.com/testcontainers/testcontainers-go - Connected to docker: 
  Server Version: 20.10.8
  API Version: 1.41
  Operating System: Ubuntu 20.04.3 LTS
  Total Memory: 10632 MB
2023/04/15 16:18:21 Failed to get image auth for docker.io. Setting empty credentials for the image: docker.io/testcontainers/ryuk:0.3.4. Error is:credentials not found in native keychain

2023/04/15 16:19:06 Starting container id: 0d8341b2270e image: docker.io/testcontainers/ryuk:0.3.4
2023/04/15 16:19:10 Waiting for container id 0d8341b2270e image: docker.io/testcontainers/ryuk:0.3.4
2023/04/15 16:19:10 Container is ready id: 0d8341b2270e image: docker.io/testcontainers/ryuk:0.3.4
2023/04/15 16:19:28 Starting container id: 999cf02b5a82 image: redis:latest
2023/04/15 16:19:30 Waiting for container id 999cf02b5a82 image: redis:latest
2023/04/15 16:19:30 Container is ready id: 999cf02b5a82 image: redis:latest
PASS
ok   demo 73.262s