您如何测试golang命令行输出

Question

我想测试golang命令行应用程序的输出，但是我不太确定如何使用go的测试库来实现。

假设我有一个像这样的程序：

package main

import (
    "flag"
    "fmt"
)

func main() {
    const (
        cityDefault = "San Francisco"
        cityDoc     = "the city you want the forecast for"
    )
    var city string
    flag.StringVar(&city, "city", cityDefault, cityDoc)
    flag.StringVar(&city, "c", cityDefault, cityDoc)
    flag.Parse()

    fmt.Println(city)
}

我想测试这两个：

$ ./myapp -c "Los Angeles"
$ ./myapp -city "Los Angeles"

...输出Lost Angeles。因此，我想问题是，如何集成测试golang命令行应用程序的输出？

Answer 1

这是解析命令行参数的一个糟糕示例，但它显示了我用来在应用程序中测试命令行参数的框架。

主程序

package main

import (
    "log"
    "os"
)

func main() {
    var city string
    parseFlags(&city, os.Args)

    log.Println(city)
}

func parseFlags(result *string, args []string) {
    cityDefault := "San Francisco"

    switch len(args) {
    case 3:
        *result = args[2]
    default:
        *result = cityDefault
    }
}

main_unit_test.go

package main

import (
    "log"
    "testing"
)

// TestParseFlags - test our command line flags
func TestParseFlags(t *testing.T) {
    var parseFlagsTests = []struct {
        flags    []string // input flags to the command line
        expected string   // expected
    }{
        {[]string{"/fake/loc/main"}, "San Francisco"},
        {[]string{"/fake/loc/main", "-c", "Los Angeles"}, "Los Angeles"},
        {[]string{"/fake/loc/main", "--city", "Los Angeles"}, "Los Angeles"},
    }

    for _, tt := range parseFlagsTests {
        var output string
        parseFlags(&output, tt.flags)
        if output != tt.expected {
            t.Errorf("expected: %s, actual: %s", tt.expected, output)
        }
    }
}

我通常使用这个包来解析我所有应用程序中的命令行参数。我将按如下方式构建我的代码（未显示测试，但它们通常遵循上面显示的测试的要点）：

主程序

package main

import (
    "log"
    "os"

    "myDir/cli"
)

func main() {
    // Grab the user inputed CLI flags
    cliFlags := cli.FlagsStruct{}
    cliErr := cli.StartCLI(&cliFlags, os.Args)
    if cliErr != nil {
        log.Println("Error grabbing command line args")
        log.Fatal(cliErr)
    }

    // Do stuff ...
}

/myDir/cli.go

package cli

import "github.com/urfave/cli"

// FlagsStruct - holds command line args
type FlagsStruct struct {
    MyFlag string
}

// StartCLI - gathers command line args
func StartCLI(cliFlags *FlagsStruct, args []string) error {
    app := cli.NewApp()
    app.Action = func(ctx *cli.Context) error {
        MyFlag := ctx.GlobalString("my-flag")

        // build the cli struct to send back to main
        cliFlags.MyFlag = MyFlag
        return nil
    }
    app.Authors = []cli.Author{
        {
            Email: "my@email.com",
            Name:  "Adam Hanna",
        },
    }
    app.Flags = []cli.Flag{
        cli.StringFlag{
            Name:  "my-flag, f",
            Usage: "My flag usage goes here",
            Value: "myDefault",
        },
    }
    app.Name = "myAppName"
    app.Usage = "My App's Usage"
    app.Version = "0.0.1"
    return app.Run(args)
}