I came across this in the LXD test suite today, which was hard to track
down, so I figured I'd let everyone know about it.
We have a nice helper in testing.IsolationSuite with "PatchValue()" that
will change a global for you during the test, and then during TearDown()
will cleanup the patch it made.
It turns out that if your test doesn't have a pointer receiver this fails,
because the "suite" object is a copy, so when PatchValue calls AddCleanup
to do s.testStack = append(...) the suite object goes away before TearDown
is called.
You can see this with the attached test suite.
Example:
func (s mySuite) TestFoo(c *gc.C) {
// This is unsafe because s.PatchValue ends up modifying s.testStack but
that attribute only exists
// for the life of the TestFoo function
s.PatchValue(&globalVar, "newvalue")
}
I tried adding the attached patch so that we catch places we are using
AddCleanup unsafely, but it fails a few tests I wasn't expecting, so I'm
not sure if I'm actually doing the right thing.
John
=:->
diff --git a/cleanup.go b/cleanup.go
index 48a48bb..2b88f7e 100644
--- a/cleanup.go
+++ b/cleanup.go
@@ -18,10 +18,13 @@ type cleanupStack []CleanupFunc
type CleanupSuite struct {
testStack cleanupStack
suiteStack cleanupStack
+ suiteSuite *CleanupSuite
+ testSuite *CleanupSuite
}
func (s *CleanupSuite) SetUpSuite(c *gc.C) {
s.suiteStack = nil
+ s.suiteSuite = s
}
func (s *CleanupSuite) TearDownSuite(c *gc.C) {
@@ -30,6 +33,7 @@ func (s *CleanupSuite) TearDownSuite(c *gc.C) {
func (s *CleanupSuite) SetUpTest(c *gc.C) {
s.testStack = nil
+ s.testSuite = s
}
func (s *CleanupSuite) TearDownTest(c *gc.C) {
@@ -45,12 +49,18 @@ func (s *CleanupSuite) callStack(c *gc.C, stack
cleanupStack) {
// AddCleanup pushes the cleanup function onto the stack of functions to be
// called during TearDownTest.
func (s *CleanupSuite) AddCleanup(cleanup CleanupFunc) {
+ if s != s.testSuite {
+ panic("testSuite changed from SetUp to TearDown")
+ }
s.testStack = append(s.testStack, cleanup)
}
// AddSuiteCleanup pushes the cleanup function onto the stack of functions to
// be called during TearDownSuite.
func (s *CleanupSuite) AddSuiteCleanup(cleanup CleanupFunc) {
+ if s != s.testSuite {
+ panic("test suite changed from SetUpSuite before
AddSuiteCleanup")
+ }
s.suiteStack = append(s.suiteStack, cleanup)
}
package lxdclient_test
import (
"github.com/juju/testing"
gc "gopkg.in/check.v1"
)
var global string = "original"
type nonPointer struct {
testing.IsolationSuite
}
var _ = gc.Suite(&nonPointer{})
type pointer struct {
testing.IsolationSuite
}
var _ = gc.Suite(&pointer{})
func (n nonPointer) TestPatchGlobal(c *gc.C) {
n.PatchValue(&global, "patched")
c.Assert(global, gc.Equals, "patched")
}
func (n nonPointer) TestUnpatchedGlobal(c *gc.C) {
// Will fail if TestPatchGlobal runs first
c.Assert(global, gc.Equals, "original")
}
func (p *pointer) TestPatchGlobal(c *gc.C) {
p.PatchValue(&global, "patched")
c.Assert(global, gc.Equals, "patched")
}
func (p *pointer) TestPatchedGlobal(c *gc.C) {
// Should always pass, unless nonPointer.TestPatchGlobal runs first
c.Assert(global, gc.Equals, "original")
}
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