如何在go测试中检查日志/输出? [英] How to check a log/output in go test?

问题描述

在某些情况下，我具有记录错误的功能:

I have this function that logs the error in some cases:

func readByte(/*...*/){
    // ...
    if err != nil {
        fmt.Println("ERROR")
        log.Print("Couldn't read first byte")
        return
    }
    // ...
}

现在，在测试文件中，我要检查此函数的输出错误:

Now, in the test file, I want to check the output error from this function:

    c.Assert(OUTPUT, check.Matches, "teste")

如何访问日志?我试图放置一个缓冲区，但是没有用.在不更改我的readByte函数代码的情况下捕获此日志的正确方法是什么?

How can I access the log? I tried to put a buffer but it didn't work. What is the right way to catch this log without change my readByte function code?

推荐答案

例如，

readbyte_test.go :

package main

import (
    "bytes"
    "fmt"
    "io"
    "log"
    "os"
    "testing"
)

func readByte( /*...*/ ) {
    // ...
    err := io.EOF // force an error
    if err != nil {
        fmt.Println("ERROR")
        log.Print("Couldn't read first byte")
        return
    }
    // ...
}

func TestReadByte(t *testing.T) {
    var buf bytes.Buffer
    log.SetOutput(&buf)
    defer func() {
        log.SetOutput(os.Stderr)
    }()
    readByte()
    t.Log(buf.String())
}

输出:

$ go test -v readbyte_test.go 
=== RUN   TestReadByte
ERROR
--- PASS: TestReadByte (0.00s)
    readbyte_test.go:30: 2017/05/22 16:41:00 Couldn't read first byte
PASS
ok      command-line-arguments  0.004s
$ 

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