我刚刚学习了使用 exec.Command() 的单元测试函数，即模拟 exec.Command()。我继续添加更多单元案例，但遇到了无法针对不同场景模拟输出的问题。

这是一个示例代码 hello.go 我正在尝试测试...

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())
}

下面是测试代码hello_test.go...

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 第二次测试失败 TestPrintDateUnableToRunError...

$ 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

即使我尝试在测试用例中设置全局 mockedDate 值，它仍然会获得初始化时使用的全局值。 全局值没有设置？或者对全局变量的更改未在 TestHelperProcess 中更新？

最佳答案

我找到了解决方案...

Is the global value not getting set? Or the changes to that global var is not getting updated in TestHelperProcess?

由于在 TestPrintDate() 中，调用了 fakeExecCommand 而不是 exec.Command，调用 fakeExecCommand 运行 go test 只运行 TestHelperProcess()，这完全是一个新的调用，其中只会执行 TestHelperProcess()。由于仅调用了 TestHelperProcess()，因此未设置全局变量。

解决方案是在 fakeExecCommand 中设置 Env，并在 TestHelperProcess() 中检索它并返回这些值。

PS> TestHelperProcess 重命名为 TestExecCommandHelper，并重命名了几个变量。

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))
    }
}

去测试 结果如下... (故意让一项测试失败以表明模拟工作正常)。

 go test hello
--- FAIL: TestPrintDate (0.01s)
        hello_test.go:45: Expected "Sun Aug 20", got "Sun Aug 201"
FAIL
FAIL    hello   0.018s

关于unit-testing - 如何在 Go lang 中模拟 exec.Command 进行多个单元测试？，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/45789101/