1 files changed, 71 insertions, 0 deletions
diff --git a/pkg/sync/mutex_test.go b/pkg/sync/mutex_test.go
new file mode 100644
index 000000000..0838248b4
--- /dev/null
+++ b/pkg/sync/mutex_test.go
@@ -0,0 +1,71 @@
+// Copyright 2019 The gVisor Authors.
+//
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package sync
+
+import (
+	"sync"
+	"testing"
+	"unsafe"
+)
+
+// TestStructSize verifies that syncMutex's size hasn't drifted from the
+// standard library's version.
+//
+// The correctness of this package relies on these remaining in sync.
+func TestStructSize(t *testing.T) {
+	const (
+		got  = unsafe.Sizeof(syncMutex{})
+		want = unsafe.Sizeof(sync.Mutex{})
+	)
+	if got != want {
+		t.Errorf("got sizeof(syncMutex) = %d, want = sizeof(sync.Mutex) = %d", got, want)
+	}
+}
+
+// TestFieldValues verifies that the semantics of syncMutex.state from the
+// standard library's implementation.
+//
+// The correctness of this package relies on these remaining in sync.
+func TestFieldValues(t *testing.T) {
+	var m Mutex
+	m.Lock()
+	if got := *m.state(); got != mutexLocked {
+		t.Errorf("got locked sync.Mutex.state = %d, want = %d", got, mutexLocked)
+	}
+	m.Unlock()
+	if got := *m.state(); got != mutexUnlocked {
+		t.Errorf("got unlocked sync.Mutex.state = %d, want = %d", got, mutexUnlocked)
+	}
+}
+
+func TestDoubleTryLock(t *testing.T) {
+	var m Mutex
+	if !m.TryLock() {
+		t.Fatal("failed to aquire lock")
+	}
+	if m.TryLock() {
+		t.Fatal("unexpectedly succeeded in aquiring locked mutex")
+	}
+}
+
+func TestTryLockAfterLock(t *testing.T) {
+	var m Mutex
+	m.Lock()
+	if m.TryLock() {
+		t.Fatal("unexpectedly succeeded in aquiring locked mutex")
+	}
+}
+
+func TestTryLockUnlock(t *testing.T) {
+	var m Mutex
+	if !m.TryLock() {
+		t.Fatal("failed to aquire lock")
+	}
+	m.Unlock()
+	if !m.TryLock() {
+		t.Fatal("failed to aquire lock after unlock")
+	}
+}