Add tests for native GetFileOwner

src/libpsl-native/test/CMakeLists.txt

@@ -1,6 +1,7 @@
 add_subdirectory(googletest)
 
 add_executable(psl-native-test
+  test-getfileowner.cpp
   test-locale.cpp
   test-getcurrentprocessid.cpp
   test-getusername.cpp

src/libpsl-native/test/test-getfileowner.cpp

@@ -0,0 +1,32 @@
+//! @file test-getfileowner.cpp
+//! @author Andrew Schwartzmeyer <andschwa@microsoft.com>
+//! @brief Tests GetFileOwner
+
+#include <gtest/gtest.h>
+#include <errno.h>
+#include <unistd.h>
+#include "getfileowner.h"
+
+using namespace std;
+
+//! Test fixture for GetFileOwner
+class GetFileOwnerTest : public ::testing::Test
+{
+};
+
+TEST_F(GetFileOwnerTest, CanGetOwnerOfRoot)
+{
+    ASSERT_STREQ(GetFileOwner("/"), "root");
+}
+
+TEST_F(GetFileOwnerTest, CannotGetOwnerOfFakeFile)
+{
+    EXPECT_STREQ(GetFileOwner("SomeMadeUpFileNameThatDoesNotExist"), NULL);
+    EXPECT_EQ(errno, ERROR_FILE_NOT_FOUND);
+}
+
+TEST_F(GetFileOwnerTest, ReturnsNullForNullInput)
+{
+    EXPECT_STREQ(GetFileOwner(NULL), NULL);
+    EXPECT_EQ(errno, ERROR_INVALID_PARAMETER);
+}