tests: procfs: clean up mock test hook

To make the code a little easier to follow, add some actual dummy
functions that we assign to rather than re-using previous functions in a
confusing way.

Fixes: 6864912 ("Isolate the testing import in test code")
Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>

procfs_linux.go

@@ -425,17 +425,16 @@ func checkProcSelfFdPath(path string, file *os.File) error {
 	return nil
 }
 
-// Test hooks
-var hookForcePrivateProcRootOpenTree = func(_ *os.File) bool {
-	return false
-}
-
-var hookForcePrivateProcRootOpenTreeAtRecursive = hookForcePrivateProcRootOpenTree
-
-var hookForceGetProcRootUnsafe = func() bool {
-	return false
-}
+// Test hooks used in the procfs tests to verify that the fallback logic works.
+// See testing_mocks_linux_test.go and procfs_linux_test.go for more details.
+var (
+	hookForcePrivateProcRootOpenTree            = hookDummyFile
+	hookForcePrivateProcRootOpenTreeAtRecursive = hookDummyFile
+	hookForceGetProcRootUnsafe                  = hookDummy
 
-var hookForceProcSelfTask = hookForceGetProcRootUnsafe
+	hookForceProcSelfTask = hookDummy
+	hookForceProcSelf     = hookDummy
+)
 
-var hookForceProcSelf = hookForceGetProcRootUnsafe
+func hookDummy() bool               { return false }
+func hookDummyFile(_ *os.File) bool { return false }

procfs_linux_test.go

@@ -418,3 +418,8 @@ func TestVerifyProcRoot_NotProc(t *testing.T) {
 		testVerifyProcRoot(t, t.TempDir(), errUnsafeProcfs, "incorrect procfs root filesystem type")
 	})
 }
+
+func TestProcfsDummyHooks(t *testing.T) {
+	assert.False(t, hookDummy(), "hookDummy should always return false")
+	assert.False(t, hookDummyFile(nil), "hookDummyFile should always return false")
+}

testing_mocks_linux_test.go

@@ -71,6 +71,7 @@ func init() {
 	hookForceGetProcRootUnsafe = testingForceGetProcRootUnsafe
 	hookForcePrivateProcRootOpenTree = testingForcePrivateProcRootOpenTree
 	hookForcePrivateProcRootOpenTreeAtRecursive = testingForcePrivateProcRootOpenTreeAtRecursive
+
 	hookForceProcSelf = testingForceProcSelf
 	hookForceProcSelfTask = testingForceProcSelfTask
 }