diff --git a/pkg/sentry/vfs/BUILD b/pkg/sentry/vfs/BUILD
index e17e9af41..4aa86996a 100644
--- a/pkg/sentry/vfs/BUILD
+++ b/pkg/sentry/vfs/BUILD
@@ -115,6 +115,7 @@ go_library(
         "anonfs.go",
         "context.go",
         "debug.go",
+        "debug_testonly.go",
         "dentry.go",
         "device.go",
         "epoll.go",
diff --git a/pkg/sentry/vfs/debug.go b/pkg/sentry/vfs/debug.go
index 0ed20f249..53cac1fd9 100644
--- a/pkg/sentry/vfs/debug.go
+++ b/pkg/sentry/vfs/debug.go
@@ -12,11 +12,14 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+//go:build !check_invariants
+// +build !check_invariants
+
 package vfs
 
 const (
 	// If checkInvariants is true, perform runtime checks for invariants
-	// expected by the vfs package. This is normally disabled since VFS is
-	// often a hot path.
+	// expected by the vfs package. This is disabled for non-test binaries since
+	// VFS is often a hot path.
 	checkInvariants = false
 )
diff --git a/pkg/sentry/vfs/debug_testonly.go b/pkg/sentry/vfs/debug_testonly.go
new file mode 100644
index 000000000..6c6158b43
--- /dev/null
+++ b/pkg/sentry/vfs/debug_testonly.go
@@ -0,0 +1,23 @@
+// Copyright 2019 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//go:build check_invariants
+// +build check_invariants
+
+package vfs
+
+const (
+	// Set checkInvariants to true for tests.
+	checkInvariants = true
+)
diff --git a/tools/bazeldefs/tags.bzl b/tools/bazeldefs/tags.bzl
index 6564c3b25..80dfc6f2c 100644
--- a/tools/bazeldefs/tags.bzl
+++ b/tools/bazeldefs/tags.bzl
@@ -49,12 +49,13 @@ generic = [
     "_norace",
     "_unsafe",
     "_opts",
+    "_testonly",
 ]
 
 # State explosion? Sure. This is approximately:
-#   len(archs) * (1 + 2 * len(oses) * (1 + 2 * len(generic))
+#   len(archs) * (1 + 2 * len(oses)) * (1 + 2 * len(generic))
 #
-# This evaluates to 495 at the time of writing. So it's a lot of different
+# This evaluates to 663 at the time of writing. So it's a lot of different
 # combinations, but not so much that it will cause issues. We can probably add
 # quite a few more variants before this becomes a genuine problem.
 go_suffixes = explode(explode(archs, oses), generic)