Unit testing 如何在Go lang中模拟多个单元测试的exec.Command？

我刚刚学习了使用

exec.Command（）

的单元测试函数，即模拟

exec.Command（）

。我继续添加了更多的单元案例，但遇到了无法模拟不同场景的输出的问题

这是一个示例代码

你好。去吧

我正在测试…

package main

import (
    "fmt"
    "os/exec"
)

var execCommand = exec.Command

func printDate() ([]byte, error) {
    cmd := execCommand("date")
    out, err := cmd.CombinedOutput()
    return out, err
}

func main() {
    fmt.Printf("hello, world\n")
    fmt.Println(printDate())
}

package main

import (
    "fmt"
    "os"
    "os/exec"
    "testing"
)

var mockedExitStatus = 1
var mockedDate = "Sun Aug 20"
var expDate = "Sun Aug 20"

func fakeExecCommand(command string, args ...string) *exec.Cmd {
    cs := []string{"-test.run=TestHelperProcess", "--", command}
    cs = append(cs, args...)
    cmd := exec.Command(os.Args[0], cs...)
    cmd.Env = []string{"GO_WANT_HELPER_PROCESS=1"}
    return cmd
}

func TestHelperProcess(t *testing.T) {
    if os.Getenv("GO_WANT_HELPER_PROCESS") != "1" {
        return
    }

    // println("Mocked Data:", mockedDate)
    fmt.Fprintf(os.Stdout, mockedDate)
    os.Exit(mockedExitStatus)
}

func TestPrintDate(t *testing.T) {
    execCommand = fakeExecCommand
    defer func() { execCommand = exec.Command }()

    out, err := printDate()
    print("Std out: ", string(out))
    if err != nil {
        t.Errorf("Expected nil error, got %#v", err)
    }
    if string(out) != expDate {
        t.Errorf("Expected %q, got %q", expDate, string(out))
    }
}

func TestPrintDateUnableToRunError(t *testing.T) {
    execCommand = fakeExecCommand
    defer func() { execCommand = exec.Command }()

    mockedExitStatus = 1
    mockedDate = "Unable to run date command"
    expDate = "Unable to run date command"

    out, err := printDate()
    print("Std out: ", string(out))
    if err != nil {
        t.Errorf("Expected nil error, got %#v", err)
    }
    if string(out) != expDate {
        t.Errorf("Expected %q, got %q", expDate, string(out))
    }
}

$ go test hello
Std out: Sun Aug 20Std out: Sun Aug 20--- FAIL: TestPrintDateTomorrow (0.01s)
    hello_test.go:62: Expected "Unable to run date command", got "Sun Aug 20"
FAIL
FAIL    hello   0.017s

下面是测试代码

hello\u test.go

…

package main

import (
    "fmt"
    "os/exec"
)

var execCommand = exec.Command

func printDate() ([]byte, error) {
    cmd := execCommand("date")
    out, err := cmd.CombinedOutput()
    return out, err
}

func main() {
    fmt.Printf("hello, world\n")
    fmt.Println(printDate())
}

package main

import (
    "fmt"
    "os"
    "os/exec"
    "testing"
)

var mockedExitStatus = 1
var mockedDate = "Sun Aug 20"
var expDate = "Sun Aug 20"

func fakeExecCommand(command string, args ...string) *exec.Cmd {
    cs := []string{"-test.run=TestHelperProcess", "--", command}
    cs = append(cs, args...)
    cmd := exec.Command(os.Args[0], cs...)
    cmd.Env = []string{"GO_WANT_HELPER_PROCESS=1"}
    return cmd
}

func TestHelperProcess(t *testing.T) {
    if os.Getenv("GO_WANT_HELPER_PROCESS") != "1" {
        return
    }

    // println("Mocked Data:", mockedDate)
    fmt.Fprintf(os.Stdout, mockedDate)
    os.Exit(mockedExitStatus)
}

func TestPrintDate(t *testing.T) {
    execCommand = fakeExecCommand
    defer func() { execCommand = exec.Command }()

    out, err := printDate()
    print("Std out: ", string(out))
    if err != nil {
        t.Errorf("Expected nil error, got %#v", err)
    }
    if string(out) != expDate {
        t.Errorf("Expected %q, got %q", expDate, string(out))
    }
}

func TestPrintDateUnableToRunError(t *testing.T) {
    execCommand = fakeExecCommand
    defer func() { execCommand = exec.Command }()

    mockedExitStatus = 1
    mockedDate = "Unable to run date command"
    expDate = "Unable to run date command"

    out, err := printDate()
    print("Std out: ", string(out))
    if err != nil {
        t.Errorf("Expected nil error, got %#v", err)
    }
    if string(out) != expDate {
        t.Errorf("Expected %q, got %q", expDate, string(out))
    }
}

$ go test hello
Std out: Sun Aug 20Std out: Sun Aug 20--- FAIL: TestPrintDateTomorrow (0.01s)
    hello_test.go:62: Expected "Unable to run date command", got "Sun Aug 20"
FAIL
FAIL    hello   0.017s

go test

第二次测试失败

TestPrintDateUnableToRunError

..

package main

import (
    "fmt"
    "os/exec"
)

var execCommand = exec.Command

func printDate() ([]byte, error) {
    cmd := execCommand("date")
    out, err := cmd.CombinedOutput()
    return out, err
}

func main() {
    fmt.Printf("hello, world\n")
    fmt.Println(printDate())
}

package main

import (
    "fmt"
    "os"
    "os/exec"
    "testing"
)

var mockedExitStatus = 1
var mockedDate = "Sun Aug 20"
var expDate = "Sun Aug 20"

func fakeExecCommand(command string, args ...string) *exec.Cmd {
    cs := []string{"-test.run=TestHelperProcess", "--", command}
    cs = append(cs, args...)
    cmd := exec.Command(os.Args[0], cs...)
    cmd.Env = []string{"GO_WANT_HELPER_PROCESS=1"}
    return cmd
}

func TestHelperProcess(t *testing.T) {
    if os.Getenv("GO_WANT_HELPER_PROCESS") != "1" {
        return
    }

    // println("Mocked Data:", mockedDate)
    fmt.Fprintf(os.Stdout, mockedDate)
    os.Exit(mockedExitStatus)
}

func TestPrintDate(t *testing.T) {
    execCommand = fakeExecCommand
    defer func() { execCommand = exec.Command }()

    out, err := printDate()
    print("Std out: ", string(out))
    if err != nil {
        t.Errorf("Expected nil error, got %#v", err)
    }
    if string(out) != expDate {
        t.Errorf("Expected %q, got %q", expDate, string(out))
    }
}

func TestPrintDateUnableToRunError(t *testing.T) {
    execCommand = fakeExecCommand
    defer func() { execCommand = exec.Command }()

    mockedExitStatus = 1
    mockedDate = "Unable to run date command"
    expDate = "Unable to run date command"

    out, err := printDate()
    print("Std out: ", string(out))
    if err != nil {
        t.Errorf("Expected nil error, got %#v", err)
    }
    if string(out) != expDate {
        t.Errorf("Expected %q, got %q", expDate, string(out))
    }
}

$ go test hello
Std out: Sun Aug 20Std out: Sun Aug 20--- FAIL: TestPrintDateTomorrow (0.01s)
    hello_test.go:62: Expected "Unable to run date command", got "Sun Aug 20"
FAIL
FAIL    hello   0.017s

---

即使我试图在测试用例中设置global

mockedDate

值，它仍然会得到初始化时使用的全局值是否未设置全局值？或者在

TestHelperProcess

？

中没有更新对该全局变量的更改，根据您发布的代码，

mockedDate

变量没有任何作用。无论是测试还是对

printDate（）

的调用都没有使用它，因此

TestPrintDateUnableToRunError（）

测试的执行与之前的测试一样

如果要将功能添加到

printDate（）

函数以返回字符串“无法运行日期命令”（在这种情况下），则第62行的条件将通过。也就是说，如果

printDate（）

的返回值中有错误，则不需要进行此类检查。如果返回的错误为非nil，则返回的输出字符串应无效（或为空，

“”

）

---

我不知道你到底想让

printDate（）

失败，但就目前情况而言，它无法返回你在

TestPrintDateUnableToRunError（）

中期望的值。我找到了解决方案

是否未设置全局值？或者对该全局变量的更改没有在TestHelperProcess中得到更新

由于在

TestPrintDate（）

中，调用了

fakeExecCommand

而不是exec.Command，并且调用

fakeExecCommand

运行

go test

以仅运行

TestHelperProcess（）

，因此这是一个新的调用，其中只执行

TestHelperProcess（）

。因为只调用了

TestHelperProcess（）

，所以没有设置全局变量

解决方案是在

fakeExecCommand

中设置Env，然后在

TestHelperProcess（）

中检索该Env并返回这些值

PS>

TestHelperProcess

重命名为

TestExecCommandHelper

，并且很少有变量被重命名

package main

import (
    "fmt"
    "os"
    "os/exec"
    "strconv"
    "testing"
)

var mockedExitStatus = 0
var mockedStdout string

func fakeExecCommand(command string, args ...string) *exec.Cmd {
    cs := []string{"-test.run=TestExecCommandHelper", "--", command}
    cs = append(cs, args...)
    cmd := exec.Command(os.Args[0], cs...)
    es := strconv.Itoa(mockedExitStatus)
    cmd.Env = []string{"GO_WANT_HELPER_PROCESS=1",
        "STDOUT=" + mockedStdout,
        "EXIT_STATUS=" + es}
    return cmd
}

func TestExecCommandHelper(t *testing.T) {
    if os.Getenv("GO_WANT_HELPER_PROCESS") != "1" {
        return
    }

    // println("Mocked stdout:", os.Getenv("STDOUT"))
    fmt.Fprintf(os.Stdout, os.Getenv("STDOUT"))
    i, _ := strconv.Atoi(os.Getenv("EXIT_STATUS"))
    os.Exit(i)
}

func TestPrintDate(t *testing.T) {
    mockedExitStatus = 1
    mockedStdout = "Sun Aug 201"
    execCommand = fakeExecCommand
    defer func() { execCommand = exec.Command }()
    expDate := "Sun Aug 20"

    out, _ := printDate()
    if string(out) != expDate {
        t.Errorf("Expected %q, got %q", expDate, string(out))
    }
}

func TestPrintDateUnableToRunError(t *testing.T) {
    mockedExitStatus = 1
    mockedStdout = "Unable to run date command"
    execCommand = fakeExecCommand
    defer func() { execCommand = exec.Command }()

    expDate := "Unable to run date command"

    out, _ := printDate()
    // println("Stdout: ", string(out))
    if string(out) != expDate {
        t.Errorf("Expected %q, got %q", expDate, string(out))
    }
}

进行测试

结果如下…… （故意不通过一次测试，以表明模拟正常工作）

---

我试图调用一些脚本，实际上，该脚本有时可能不存在。。。在这里提问，我只是以日期为例。。。谢谢顺便说一句后来我意识到我可以通过使用ENV变量来实现这一点。