TestMain-没有要运行的测试

Question

I am writing a package which compiles a C source file and writes the output to another file. I am writing tests for this package, and I need to create a temporary directory to write the output files. I am using TestMain function to do this. For some reason, I always get the warning "no tests to run" when I just run the TestMain test. I tried to debug the TestMain function and I can see that the temporary directory is indeed created. When I create the testoutput directory manually, all tests pass.

I am loading two C source files from testdata directory, one of which is intentionally wrong.

gcc.go:

package gcc

import (
    "os/exec"
)

func Compile(inPath, outPath string) error {
    cmd := exec.Command("gcc", inPath, "-o", outPath)
    return cmd.Run()
}

gcc_test.go:

package gcc

import (
    "os"
    "path/filepath"
    "testing"
)

func TestOuputFileCreated(t *testing.T) {
    var inFile = filepath.Join("testdata", "correct.c")
    var outFile = filepath.Join("testoutput", "correct_out")

    if err := Compile(inFile, outFile); err != nil {
        t.Errorf("Expected err to be nil, got %s", err.Error())
    }

    if _, err := os.Stat(outFile); os.IsNotExist(err) {
        t.Error("Expected output file to be created")
    }
}

func TestOuputFileNotCreatedForIncorrectSource(t *testing.T) {
    var inFile = filepath.Join("testdata", "wrong.c")
    var outFile = filepath.Join("testoutput", "wrong_out")

    if err := Compile(inFile, outFile); err == nil {
        t.Errorf("Expected err to be nil, got %v", err)
    }

    if _, err := os.Stat(outFile); os.IsExist(err) {
        t.Error("Expected output file to not be created")
    }
}

func TestMain(m *testing.M) {
    os.Mkdir("testoutput", 666)
    code := m.Run()
    os.RemoveAll("testoutput")
    os.Exit(code)
}

go test output:

sriram@sriram-Vostro-15:~/go/src/github.com/sriram-kailasam/relab/pkg/gcc$ go test
--- FAIL: TestOuputFileCreated (0.22s)
        gcc_test.go:14: Expected err to be nil, got exit status 1
FAIL
FAIL    github.com/sriram-kailasam/relab/pkg/gcc        0.257s

Running TestMain:

Running tool: /usr/bin/go test -timeout 30s github.com/sriram-kailasam/relab/pkg/gcc -run ^(TestMain)$

ok      github.com/sriram-kailasam/relab/pkg/gcc    0.001s [no tests to run]
Success: Tests passed.

Answer 1

Odds are, your problems are around the mode value you're passing to os.Mkdir(...). You're providing 666 decimal, which is 01232 octal (or if you prefer, a permissions string of d-w--wx-wT) which I assume is not really what you're looking for.

Instead of 666, you should specify 0666 -- the leading 0 indicates your value is in octal notation.

---

Also, your two tests are virtually identical; instead of using a TestMain(...) to perform your setup, I'd suggest using *T.Run(...) to execute your tests from a single, top-level Test* func. Something like this:

gcc_test.go:

package gcc

import (
  "testing"
  "path/filepath"
  "os"
)

const testoutput = "testoutput"

type testcase struct {
  inFile  string
  outFile string
  err     error
}

func (tc *testcase) test(t *testing.T) {
  var (
    in  = filepath.Join("testdata", tc.inFile)
    out = filepath.Join(testoutput, tc.outFile)
  )

  if err := Compile(in, out); err != tc.err {
    t.Errorf("Compile(%q, %q) == %v; Wanted %v", in, out, err, tc.err)
  }
}

func TestCompile(t *testing.T) {
  os.Mkdir(testoutput, 0666)

  tests := map[string]*testcase{
    "correct": &testcase{"correct.c", "correct_out", nil},
    "wrong":   &testcase{"wrong.c", "wrong_out", expectedError},
  }

  for name, tc := range tests {
    t.Run(name, tc.test)
  }
}