Bad CopyWalker

test_test.go

package main

import (
	"io"
	"io/ioutil"
	"os"
	"reflect"
	"strings"
	"testing"
)

const v1 = `
This
is
my
test
data
of
version
1
`

const v2 = `
Version
2
`

func TestCopyWalker(t *testing.T) {
	// Create temp file to test on.
	tmpfile, err := ioutil.TempFile("", "example")
	if err != nil {
		t.Fatalf("Creating temp file should succeed, got: %v", err)
	}

	defer os.Remove(tmpfile.Name())

	foo(t, tmpfile.Name(), v1)

	foo(t, tmpfile.Name(), v2)
}

func foo(t *testing.T, p string, data string) {
	// Re-implement CopyingWalker.
	targetFile, err := os.OpenFile(p, os.O_RDWR|os.O_CREATE, 0644)
	if err != nil {
		t.Fatalf("Opening tmp file %s should succeed, got: %v", p, err)
	}

	defer targetFile.Close()

	if _, err := io.Copy(targetFile, strings.NewReader(data)); err != nil {
		t.Fatalf("Writing to tmp file should succeed, got: %v", err)
	}

	// Read the file to make sure we wrote correct output.
	dataRead, err := ioutil.ReadFile(p)
	if err != nil {
		t.Fatalf("Reading tmp file should succeed, got: %v", err)
	}

	if !reflect.DeepEqual(data, string(dataRead)) {
		t.Fatalf("expected:\n===\n%s\n===\n, got:\n===\n%s\n===\n", data, dataRead)
	}
}

Results as expected:

--- FAIL: TestCopyWalker (0.00s)
    test_test.go:62: expected:
        ===
        
        Version
        2
        
        ===
        , got:
        ===
        
        Version
        2
        
        test
        data
        of
        version
        1
        
        ===
FAIL
exit status 1
FAIL	foo	0.001s