add a test that fails if MemMapFs has the same `at` counter for multiple file objects
diff --git a/memmap_test.go b/memmap_test.go
index ce9a4e5..b739927 100644
--- a/memmap_test.go
+++ b/memmap_test.go
@@ -100,3 +100,53 @@
t.Error(op+":", err, "contains another os.PathError")
}
}
+
+// Fails if multiple file objects use the same file.at counter in MemMapFs
+func TestMultipleOpenFiles(t *testing.T) {
+ defer removeAllTestFiles(t)
+ const fileName = "./afero-demo2.txt"
+
+ var fss = []Fs{&OsFs{}, &MemMapFs{}}
+ var data = make([][]byte, len(fss))
+
+ for i, fs := range fss {
+ dir := testDir(fs)
+ path := filepath.Join(dir, fileName)
+ fh1, err := fs.Create(path)
+ if err != nil {
+ t.Error("os.Create failed: " + err.Error())
+ }
+ _, err = fh1.Write([]byte("test"))
+ if err != nil {
+ t.Error("fh.Write failed: " + err.Error())
+ }
+ fh1.Seek(0, os.SEEK_SET)
+
+ fh2, err := fs.OpenFile(path, os.O_RDWR, 0777)
+ if err != nil {
+ t.Error("fs.OpenFile failed: " + err.Error())
+ }
+ fh2.Seek(0, os.SEEK_END)
+ fh2.Write([]byte("data"))
+ fh2.Close()
+
+ fh1.Write([]byte("data"))
+ fh1.Close()
+ // the file now should contain "datadata"
+ data[i], err = ReadFile(fs, path)
+ if err != nil {
+ t.Error(err)
+ }
+ }
+
+ for i, fs := range fss {
+ if i == 0 {
+ continue
+ }
+ if string(data[0]) != string(data[i]) {
+ t.Errorf("OsFs and %s don't behave the same\n"+
+ "OsFs: \"%s\"\n%s: \"%s\"\n",
+ fs.Name(), data[0], fs.Name(), data[i])
+ }
+ }
+}
