OSCrypt for POSIX uses libsecret to store a randomised encryption key.

components/os_crypt/os_crypt_unittest.cc

Index: components/os_crypt/os_crypt_unittest.cc
diff --git a/components/os_crypt/os_crypt_unittest.cc b/components/os_crypt/os_crypt_unittest.cc
index 9837cbc29a0d8d1725056fdd79006e3e9e54e2ed..50fb12bc46ed9d3483f289b6e3101e59cb802578 100644
--- a/components/os_crypt/os_crypt_unittest.cc
+++ b/components/os_crypt/os_crypt_unittest.cc
@@ -13,6 +13,10 @@
 #include "build/build_config.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
+#if defined(USE_LIBSECRET)
+#include "components/os_crypt/os_crypt_mocker_linux.h"
+#endif
+
 namespace {
 
 class OSCryptTest : public testing::Test {
@@ -23,6 +27,15 @@ class OSCryptTest : public testing::Test {
 #if defined(OS_MACOSX)
     OSCrypt::UseMockKeychain(true);
 #endif
+#if defined(USE_LIBSECRET)
+    OSCryptMockerLinux::SetUpWithSingleton();
+#endif
+  }
+
+  void TearDown() override {
+#if defined(USE_LIBSECRET)
+    OSCryptMockerLinux::TearDown();
+#endif
   }
 
  private: