使用 Go 进行单元测试

简介

日常开发中, 测试是不能缺少的.

Go 标准库中有一个叫做 testing 的测试框架, 可以用于单元测试和性能测试.

它是和命令 go test 集成使用的.

测试文件是以后缀 _test.go 命名的, 通常和被测试的文件放在同一个包中.

单元测试

单元测试的格式形如:

func TestAbs(t *testing.T) {
  got := Abs(-1)
  if got != 1 {
    t.Errorf("Abs(-1) = %d; want 1", got)
  }
}

在 util 目录下创建一个文件 util_test.go , 添加一个单元测试:

package util

import "testing"

// 普通的测试
func TestGenShortID(t *testing.T) {
    shortID, err := GenShortID()
    if shortID == "" || err != nil {
        t.Error("GenShortID failed")
    }
}

然后, 在根目录下运行 go test -v ./util/ , 测试结果如下:

root@592402321ce7:/workspace# go test -v ./util/
=== RUN   TestGenShortID
--- PASS: TestGenShortID (0.00s)
PASS
ok      tzh.com/web/util        0.006s

性能测试

性能测试的结果形如:

func BenchmarkHello(b *testing.B) {
  for i := 0; i < b.N; i++ {
    fmt.Sprintf("hello")
  }
}

在 util_test.go 添加性能测试:

// 性能测试
func BenchmarkGenShortID(b *testing.B) {
    for i := 0; i < b.N; i++ {
        GenShortID()
    }
}

运行结果如下(使用 --run=none 避免运行普通的测试函数, 因为一般不可能有函数名匹配 none ):

root@592402321ce7:/workspace# go test -v -bench="BenchmarkGenShortID$" --run=none ./util/
goos: linux
goarch: amd64
pkg: tzh.com/web/util
BenchmarkGenShortID-2             507237              2352 ns/op
PASS
ok      tzh.com/web/util        1.229s

这说明, 平均每次运行 GenShortID() 需要 2352 纳秒.

性能分析

运行测试的时候, 可以指定一些参数, 生成性能文件 profile.

-blockprofile block.out
    Write a goroutine blocking profile to the specified file
    when all tests are complete.
    Writes test binary as -c would.

-blockprofilerate n
    Control the detail provided in goroutine blocking profiles by
    calling runtime.SetBlockProfileRate with n.
    See 'go doc runtime.SetBlockProfileRate'.
    The profiler aims to sample, on average, one blocking event every
    n nanoseconds the program spends blocked. By default,
    if -test.blockprofile is set without this flag, all blocking events
    are recorded, equivalent to -test.blockprofilerate=1.

-coverprofile cover.out
    Write a coverage profile to the file after all tests have passed.
    Sets -cover.

-cpuprofile cpu.out
    Write a CPU profile to the specified file before exiting.
    Writes test binary as -c would.

-memprofile mem.out
    Write an allocation profile to the file after all tests have passed.
    Writes test binary as -c would.

-memprofilerate n
    Enable more precise (and expensive) memory allocation profiles by
    setting runtime.MemProfileRate. See 'go doc runtime.MemProfileRate'.
    To profile all memory allocations, use -test.memprofilerate=1.

-mutexprofile mutex.out
    Write a mutex contention profile to the specified file
    when all tests are complete.
    Writes test binary as -c would.

-mutexprofilefraction n
    Sample 1 in n stack traces of goroutines holding a
    contended mutex.

使用下面的命令, 生成 CPU 的 profile:

go test -v -bench="BenchmarkGenShortID$" --run=none -cpuprofile cpu.out ./util/

当前目录下, 应该会生成 cpu.out 文件和 util.test 文件.

使用下面的命令, 观察耗时操作:

# 进入交互模式
go tool pprof cpu.out
top

安装 Graphviz 后可以生成可视化的分析图.

apt install graphviz
go tool pprof -http=":" cpu.out

测试覆盖率

root@592402321ce7:/workspace# go test -v -coverprofile=cover.out ./util/
=== RUN   TestGenShortID
--- PASS: TestGenShortID (0.00s)
PASS
coverage: 9.1% of statements
ok      tzh.com/web/util        0.005s  coverage: 9.1% of statements

root@592402321ce7:/workspace# go tool cover -func=cover.out
tzh.com/web/util/util.go:12:    GenShortID      100.0%
tzh.com/web/util/util.go:17:    GetReqID        0.0%
tzh.com/web/util/util.go:22:    TimeToStr       0.0%
tzh.com/web/util/util.go:30:    GetTag          0.0%
total:                          (statements)    9.1%

使用 -coverprofile=cover.out 选项可以统计测试覆盖率.

使用 go tool cover -func=cover.out 可以查看更加详细的测试覆盖率结果,

统计每个函数的测试覆盖率.

总结

测试是开发中非常重要的一个环节, 用于保证软件质量, 切不可偷懒.

当前部分的代码

作为版本 v0.15.0