util/pidowner: new package to map from process ID to its user ID

util/pidowner/pidowner_test.go

@@ -0,0 +1,47 @@
+package pidowner
+
+import (
+	"math/rand"
+	"os"
+	"os/user"
+	"testing"
+)
+
+func TestOwnerOfPID(t *testing.T) {
+	id, err := OwnerOfPID(os.Getpid())
+	if err == ErrNotImplemented {
+		t.Skip(err)
+	}
+	if err != nil {
+		t.Fatal(err)
+	}
+	t.Logf("id=%q", id)
+
+	u, err := user.LookupId(id)
+	if err != nil {
+		t.Fatalf("LookupId: %v", err)
+	}
+	t.Logf("Got: %+v", u)
+}
+
+// validate that OS implementation returns ErrProcessNotFound.
+func TestNotFoundError(t *testing.T) {
+	// Try a bunch of times to stumble upon a pid that doesn't exist...
+	const tries = 50
+	for i := 0; i < tries; i++ {
+		_, err := OwnerOfPID(rand.Intn(1e9))
+		if err == ErrNotImplemented {
+			t.Skip(err)
+		}
+		if err == nil {
+			// We got unlucky and this pid existed. Try again.
+			continue
+		}
+		if err == ErrProcessNotFound {
+			// Pass.
+			return
+		}
+		t.Fatalf("Error is not ErrProcessNotFound: %T %v", err, err)
+	}
+	t.Errorf("after %d tries, couldn't find a process that didn't exist", tries)
+}