diff --git a/src/test/fspp/fuse/access/FuseAccessErrorTest.cpp b/src/test/fspp/fuse/access/FuseAccessErrorTest.cpp
index d9d29b8d..28c042a3 100644
--- a/src/test/fspp/fuse/access/FuseAccessErrorTest.cpp
+++ b/src/test/fspp/fuse/access/FuseAccessErrorTest.cpp
@@ -21,7 +21,6 @@ TEST_P(FuseAccessErrorTest, ReturnedErrorIsCorrect) {
   EXPECT_CALL(fsimpl, access(StrEq(FILENAME), _))
     .Times(1).WillOnce(Throw(FuseErrnoException(GetParam())));
 
-  int retval = AccessFileAllowError(FILENAME, 0);
-  EXPECT_EQ(GetParam(), errno);
-  EXPECT_EQ(-1, retval);
+  int error = AccessFileReturnError(FILENAME, 0);
+  EXPECT_EQ(GetParam(), error);
 }
diff --git a/src/test/fspp/fuse/access/testutils/FuseAccessTest.cpp b/src/test/fspp/fuse/access/testutils/FuseAccessTest.cpp
index 68926079..c1206ce2 100644
--- a/src/test/fspp/fuse/access/testutils/FuseAccessTest.cpp
+++ b/src/test/fspp/fuse/access/testutils/FuseAccessTest.cpp
@@ -1,13 +1,18 @@
 #include "FuseAccessTest.h"
 
 void FuseAccessTest::AccessFile(const char *filename, int mode) {
-  int retval = AccessFileAllowError(filename, mode);
-  EXPECT_EQ(0, retval);
+  int error = AccessFileReturnError(filename, mode);
+  EXPECT_EQ(0, error);
 }
 
-int FuseAccessTest::AccessFileAllowError(const char *filename, int mode) {
+int FuseAccessTest::AccessFileReturnError(const char *filename, int mode) {
   auto fs = TestFS();
 
   auto realpath = fs->mountDir() / filename;
-  return ::access(realpath.c_str(), mode);
+  int retval = ::access(realpath.c_str(), mode);
+  if (retval == 0) {
+    return 0;
+  } else {
+    return errno;
+  }
 }
diff --git a/src/test/fspp/fuse/access/testutils/FuseAccessTest.h b/src/test/fspp/fuse/access/testutils/FuseAccessTest.h
index cadc4d1a..405b7fcb 100644
--- a/src/test/fspp/fuse/access/testutils/FuseAccessTest.h
+++ b/src/test/fspp/fuse/access/testutils/FuseAccessTest.h
@@ -9,7 +9,7 @@ public:
   const char *FILENAME = "/myfile";
 
   void AccessFile(const char *filename, int mode);
-  int AccessFileAllowError(const char *filename, int mode);
+  int AccessFileReturnError(const char *filename, int mode);
 };
 
 #endif
diff --git a/src/test/fspp/fuse/createAndOpenFile/FuseCreateAndOpenErrorTest.cpp b/src/test/fspp/fuse/createAndOpenFile/FuseCreateAndOpenErrorTest.cpp
index 59ceff87..214a939c 100644
--- a/src/test/fspp/fuse/createAndOpenFile/FuseCreateAndOpenErrorTest.cpp
+++ b/src/test/fspp/fuse/createAndOpenFile/FuseCreateAndOpenErrorTest.cpp
@@ -21,17 +21,14 @@ TEST_F(FuseCreateAndOpenErrorTest, ReturnNoError) {
   //For the syscall to succeed, we also need to give an fstat implementation.
   ReturnIsFileOnFstat(1);
 
-  errno = 0;
-  int retval = CreateAndOpenFileAllowError(FILENAME, O_RDONLY);
-  EXPECT_EQ(errno, 0);
-  EXPECT_GE(retval, 0);
+  int error = CreateAndOpenFileReturnError(FILENAME, O_RDONLY);
+  EXPECT_EQ(0, error);
 }
 
 TEST_P(FuseCreateAndOpenErrorTest, ReturnError) {
   ReturnDoesntExistOnLstat(FILENAME);
   EXPECT_CALL(fsimpl, createAndOpenFile(StrEq(FILENAME), _)).Times(1).WillOnce(Throw(FuseErrnoException(GetParam())));
 
-  int retval = CreateAndOpenFileAllowError(FILENAME, O_RDONLY);
-  EXPECT_EQ(retval, -1);
-  EXPECT_EQ(GetParam(), errno);
+  int error = CreateAndOpenFileReturnError(FILENAME, O_RDONLY);
+  EXPECT_EQ(GetParam(), error);
 }
diff --git a/src/test/fspp/fuse/createAndOpenFile/testutils/FuseCreateAndOpenTest.cpp b/src/test/fspp/fuse/createAndOpenFile/testutils/FuseCreateAndOpenTest.cpp
index 2bc08a45..a7a81796 100644
--- a/src/test/fspp/fuse/createAndOpenFile/testutils/FuseCreateAndOpenTest.cpp
+++ b/src/test/fspp/fuse/createAndOpenFile/testutils/FuseCreateAndOpenTest.cpp
@@ -8,9 +8,23 @@ int FuseCreateAndOpenTest::CreateAndOpenFile(const char *filename, int flags) {
   return fd;
 }
 
+int FuseCreateAndOpenTest::CreateAndOpenFileReturnError(const char *filename, int flags) {
+  int fd = CreateAndOpenFileAllowError(filename, flags);
+  if (fd >= 0) {
+    return 0;
+  } else {
+    return -fd;
+  }
+}
+
 int FuseCreateAndOpenTest::CreateAndOpenFileAllowError(const char *filename, int flags) {
   auto fs = TestFS();
 
   auto realpath = fs->mountDir() / filename;
-  return ::open(realpath.c_str(), flags | O_CREAT);
+  int fd = ::open(realpath.c_str(), flags | O_CREAT);
+  if (fd >= 0) {
+    return fd;
+  } else {
+    return -errno;
+  }
 }
diff --git a/src/test/fspp/fuse/createAndOpenFile/testutils/FuseCreateAndOpenTest.h b/src/test/fspp/fuse/createAndOpenFile/testutils/FuseCreateAndOpenTest.h
index f81b544a..c2ce85bc 100644
--- a/src/test/fspp/fuse/createAndOpenFile/testutils/FuseCreateAndOpenTest.h
+++ b/src/test/fspp/fuse/createAndOpenFile/testutils/FuseCreateAndOpenTest.h
@@ -9,6 +9,8 @@ public:
   const char *FILENAME = "/myfile";
 
   int CreateAndOpenFile(const char *FILENAME, int flags);
+  int CreateAndOpenFileReturnError(const char *FILENAME, int flags);
+private:
   int CreateAndOpenFileAllowError(const char *FILENAME, int flags);
 };
 
diff --git a/src/test/fspp/fuse/fdatasync/FuseFdatasyncErrorTest.cpp b/src/test/fspp/fuse/fdatasync/FuseFdatasyncErrorTest.cpp
index e0eec2fb..0780f8f6 100644
--- a/src/test/fspp/fuse/fdatasync/FuseFdatasyncErrorTest.cpp
+++ b/src/test/fspp/fuse/fdatasync/FuseFdatasyncErrorTest.cpp
@@ -22,7 +22,6 @@ TEST_P(FuseFdatasyncErrorTest, ReturnedErrorIsCorrect) {
   EXPECT_CALL(fsimpl, fdatasync(0))
     .Times(1).WillOnce(Throw(FuseErrnoException(GetParam())));
 
-  int retval = FdatasyncFileAllowError(FILENAME);
-  EXPECT_EQ(GetParam(), errno);
-  EXPECT_EQ(-1, retval);
+  int error = FdatasyncFileReturnError(FILENAME);
+  EXPECT_EQ(GetParam(), error);
 }
diff --git a/src/test/fspp/fuse/fdatasync/testutils/FuseFdatasyncTest.cpp b/src/test/fspp/fuse/fdatasync/testutils/FuseFdatasyncTest.cpp
index 681894a6..69695c13 100644
--- a/src/test/fspp/fuse/fdatasync/testutils/FuseFdatasyncTest.cpp
+++ b/src/test/fspp/fuse/fdatasync/testutils/FuseFdatasyncTest.cpp
@@ -1,15 +1,20 @@
 #include "FuseFdatasyncTest.h"
 
 void FuseFdatasyncTest::FdatasyncFile(const char *filename) {
-  int retval = FdatasyncFileAllowError(filename);
-  EXPECT_EQ(0, retval);
+  int error = FdatasyncFileReturnError(filename);
+  EXPECT_EQ(0, error);
 }
 
-int FuseFdatasyncTest::FdatasyncFileAllowError(const char *filename) {
+int FuseFdatasyncTest::FdatasyncFileReturnError(const char *filename) {
   auto fs = TestFS();
 
   int fd = OpenFile(fs.get(), filename);
-  return ::fdatasync(fd);
+  int retval = ::fdatasync(fd);
+  if (retval == 0) {
+    return 0;
+  } else {
+    return errno;
+  }
 }
 
 int FuseFdatasyncTest::OpenFile(const TempTestFS *fs, const char *filename) {
diff --git a/src/test/fspp/fuse/fdatasync/testutils/FuseFdatasyncTest.h b/src/test/fspp/fuse/fdatasync/testutils/FuseFdatasyncTest.h
index f6536b24..7b04a833 100644
--- a/src/test/fspp/fuse/fdatasync/testutils/FuseFdatasyncTest.h
+++ b/src/test/fspp/fuse/fdatasync/testutils/FuseFdatasyncTest.h
@@ -9,7 +9,7 @@ public:
   const char *FILENAME = "/myfile";
 
   void FdatasyncFile(const char *filename);
-  int FdatasyncFileAllowError(const char *filename);
+  int FdatasyncFileReturnError(const char *filename);
 
 private:
   int OpenFile(const TempTestFS *fs, const char *filename);
diff --git a/src/test/fspp/fuse/flush/FuseFlushErrorTest.cpp b/src/test/fspp/fuse/flush/FuseFlushErrorTest.cpp
index 0770d954..54be24c6 100644
--- a/src/test/fspp/fuse/flush/FuseFlushErrorTest.cpp
+++ b/src/test/fspp/fuse/flush/FuseFlushErrorTest.cpp
@@ -27,6 +27,6 @@ TEST_P(FuseFlushErrorTest, ReturnErrorFromFlush) {
   int fd = OpenFile(fs.get(), FILENAME);
 
   int close_result = ::close(fd);
-  EXPECT_EQ(-1, close_result);
   EXPECT_EQ(GetParam(), errno);
+  EXPECT_EQ(-1, close_result);
 }
diff --git a/src/test/fspp/fuse/flush/testutils/FuseFlushTest.cpp b/src/test/fspp/fuse/flush/testutils/FuseFlushTest.cpp
new file mode 100644
index 00000000..1000ca56
--- /dev/null
+++ b/src/test/fspp/fuse/flush/testutils/FuseFlushTest.cpp
@@ -0,0 +1,19 @@
+#include "FuseFlushTest.h"
+
+void FuseFlushTest::OpenAndCloseFile(const std::string &filename) {
+  auto fs = TestFS();
+  int fd = OpenFile(fs.get(), filename);
+  CloseFile(fd);
+}
+
+int FuseFlushTest::OpenFile(const TempTestFS *fs, const std::string &filename) {
+  auto real_path = fs->mountDir() / filename;
+  int fd = ::open(real_path.c_str(), O_RDONLY);
+  EXPECT_GE(fd, 0) << "Opening file failed";
+  return fd;
+}
+
+void FuseFlushTest::CloseFile(int fd) {
+  int retval = ::close(fd);
+  EXPECT_EQ(0, retval);
+}
diff --git a/src/test/fspp/fuse/flush/testutils/FuseFlushTest.h b/src/test/fspp/fuse/flush/testutils/FuseFlushTest.h
index 609e7b09..7c622164 100644
--- a/src/test/fspp/fuse/flush/testutils/FuseFlushTest.h
+++ b/src/test/fspp/fuse/flush/testutils/FuseFlushTest.h
@@ -11,23 +11,9 @@ class FuseFlushTest: public FuseTest {
 public:
   const std::string FILENAME = "/myfile";
 
-  void OpenAndCloseFile(const std::string &filename) {
-    auto fs = TestFS();
-    int fd = OpenFile(fs.get(), filename);
-    CloseFile(fd);
-  }
-
-  int OpenFile(const TempTestFS *fs, const std::string &filename) {
-    auto real_path = fs->mountDir() / filename;
-    int fd = ::open(real_path.c_str(), O_RDONLY);
-    EXPECT_GE(fd, 0) << "Opening file failed";
-    return fd;
-  }
-
-  void CloseFile(int fd) {
-    int retval = ::close(fd);
-    EXPECT_EQ(0, retval);
-  }
+  void OpenAndCloseFile(const std::string &filename);
+  int OpenFile(const TempTestFS *fs, const std::string &filename);
+  void CloseFile(int fd);
 };
 
 
diff --git a/src/test/fspp/fuse/fstat/FuseFstatErrorTest.cpp b/src/test/fspp/fuse/fstat/FuseFstatErrorTest.cpp
index a8b07606..d2fa4b6d 100644
--- a/src/test/fspp/fuse/fstat/FuseFstatErrorTest.cpp
+++ b/src/test/fspp/fuse/fstat/FuseFstatErrorTest.cpp
@@ -34,7 +34,6 @@ TEST_P(FuseFstatErrorTest, ReturnedErrorCodeIsCorrect) {
 
   auto fs = TestFS();
 
-  int fd = CreateFileAllowErrors(fs.get(), FILENAME);
-  EXPECT_EQ(-1, fd);
-  EXPECT_EQ(GetParam(), errno);
+  int error = CreateFileReturnError(fs.get(), FILENAME);
+  EXPECT_EQ(GetParam(), error);
 }
diff --git a/src/test/fspp/fuse/fstat/testutils/FuseFstatTest.cpp b/src/test/fspp/fuse/fstat/testutils/FuseFstatTest.cpp
index 778ca0af..0953e26b 100644
--- a/src/test/fspp/fuse/fstat/testutils/FuseFstatTest.cpp
+++ b/src/test/fspp/fuse/fstat/testutils/FuseFstatTest.cpp
@@ -10,9 +10,23 @@ int FuseFstatTest::CreateFile(const TempTestFS *fs, const std::string &filename)
   return fd;
 }
 
+int FuseFstatTest::CreateFileReturnError(const TempTestFS *fs, const std::string &filename) {
+  int fd = CreateFileAllowErrors(fs, filename);
+  if (fd >= 0) {
+    return 0;
+  } else {
+    return -fd;
+  }
+}
+
 int FuseFstatTest::CreateFileAllowErrors(const TempTestFS *fs, const std::string &filename) {
   auto real_path = fs->mountDir() / filename;
-  return ::open(real_path.c_str(), O_RDWR | O_CREAT);
+  int fd = ::open(real_path.c_str(), O_RDWR | O_CREAT);
+  if (fd >= 0) {
+    return fd;
+  } else {
+    return -errno;
+  }
 }
 
 void FuseFstatTest::OnCreateAndOpenReturnFileDescriptor(const char *filename, int descriptor) {
diff --git a/src/test/fspp/fuse/fstat/testutils/FuseFstatTest.h b/src/test/fspp/fuse/fstat/testutils/FuseFstatTest.h
index 58a76706..c8824f6a 100644
--- a/src/test/fspp/fuse/fstat/testutils/FuseFstatTest.h
+++ b/src/test/fspp/fuse/fstat/testutils/FuseFstatTest.h
@@ -7,8 +7,10 @@
 class FuseFstatTest: public FuseTest {
 public:
   int CreateFile(const TempTestFS *fs, const std::string &filename);
-  int CreateFileAllowErrors(const TempTestFS *fs, const std::string &filename);
+  int CreateFileReturnError(const TempTestFS *fs, const std::string &filename);
   void OnCreateAndOpenReturnFileDescriptor(const char *filename, int descriptor);
+private:
+  int CreateFileAllowErrors(const TempTestFS *fs, const std::string &filename);
 };
 
 
diff --git a/src/test/fspp/fuse/fsync/FuseFsyncErrorTest.cpp b/src/test/fspp/fuse/fsync/FuseFsyncErrorTest.cpp
index ace07189..071a3332 100644
--- a/src/test/fspp/fuse/fsync/FuseFsyncErrorTest.cpp
+++ b/src/test/fspp/fuse/fsync/FuseFsyncErrorTest.cpp
@@ -22,7 +22,6 @@ TEST_P(FuseFsyncErrorTest, ReturnedErrorIsCorrect) {
   EXPECT_CALL(fsimpl, fsync(0))
     .Times(1).WillOnce(Throw(FuseErrnoException(GetParam())));
 
-  int retval = FsyncFileAllowError(FILENAME);
-  EXPECT_EQ(GetParam(), errno);
-  EXPECT_EQ(-1, retval);
+  int error = FsyncFileReturnError(FILENAME);
+  EXPECT_EQ(GetParam(), error);
 }
diff --git a/src/test/fspp/fuse/fsync/testutils/FuseFsyncTest.cpp b/src/test/fspp/fuse/fsync/testutils/FuseFsyncTest.cpp
index ba62cca9..97de440c 100644
--- a/src/test/fspp/fuse/fsync/testutils/FuseFsyncTest.cpp
+++ b/src/test/fspp/fuse/fsync/testutils/FuseFsyncTest.cpp
@@ -1,15 +1,20 @@
 #include "FuseFsyncTest.h"
 
 void FuseFsyncTest::FsyncFile(const char *filename) {
-  int retval = FsyncFileAllowError(filename);
-  EXPECT_EQ(0, retval);
+  int error = FsyncFileReturnError(filename);
+  EXPECT_EQ(0, error);
 }
 
-int FuseFsyncTest::FsyncFileAllowError(const char *filename) {
+int FuseFsyncTest::FsyncFileReturnError(const char *filename) {
   auto fs = TestFS();
 
   int fd = OpenFile(fs.get(), filename);
-  return ::fsync(fd);
+  int retval = ::fsync(fd);
+  if (retval == 0) {
+    return 0;
+  } else {
+    return errno;
+  }
 }
 
 int FuseFsyncTest::OpenFile(const TempTestFS *fs, const char *filename) {
diff --git a/src/test/fspp/fuse/fsync/testutils/FuseFsyncTest.h b/src/test/fspp/fuse/fsync/testutils/FuseFsyncTest.h
index 104f1bda..55e36303 100644
--- a/src/test/fspp/fuse/fsync/testutils/FuseFsyncTest.h
+++ b/src/test/fspp/fuse/fsync/testutils/FuseFsyncTest.h
@@ -9,7 +9,7 @@ public:
   const char *FILENAME = "/myfile";
 
   void FsyncFile(const char *filename);
-  int FsyncFileAllowError(const char *filename);
+  int FsyncFileReturnError(const char *filename);
 
 private:
   int OpenFile(const TempTestFS *fs, const char *filename);
diff --git a/src/test/fspp/fuse/ftruncate/FuseFTruncateErrorTest.cpp b/src/test/fspp/fuse/ftruncate/FuseFTruncateErrorTest.cpp
index 2fbac786..b577ce43 100644
--- a/src/test/fspp/fuse/ftruncate/FuseFTruncateErrorTest.cpp
+++ b/src/test/fspp/fuse/ftruncate/FuseFTruncateErrorTest.cpp
@@ -24,7 +24,6 @@ TEST_P(FuseFTruncateErrorTest, ReturnedErrorIsCorrect) {
   //Needed to make ::ftruncate system call return successfully
   ReturnIsFileOnFstat(0);
 
-  int retval = FTruncateFileAllowError(FILENAME, 0);
-  EXPECT_EQ(GetParam(), errno);
-  EXPECT_EQ(-1, retval);
+  int error = FTruncateFileReturnError(FILENAME, 0);
+  EXPECT_EQ(GetParam(), error);
 }
diff --git a/src/test/fspp/fuse/ftruncate/testutils/FuseFTruncateTest.cpp b/src/test/fspp/fuse/ftruncate/testutils/FuseFTruncateTest.cpp
index 36178401..7adcfa2b 100644
--- a/src/test/fspp/fuse/ftruncate/testutils/FuseFTruncateTest.cpp
+++ b/src/test/fspp/fuse/ftruncate/testutils/FuseFTruncateTest.cpp
@@ -1,15 +1,20 @@
 #include "FuseFTruncateTest.h"
 
 void FuseFTruncateTest::FTruncateFile(const char *filename, off_t size) {
-  int retval = FTruncateFileAllowError(filename, size);
-  EXPECT_EQ(0, retval);
+  int error = FTruncateFileReturnError(filename, size);
+  EXPECT_EQ(0, error);
 }
 
-int FuseFTruncateTest::FTruncateFileAllowError(const char *filename, off_t size) {
+int FuseFTruncateTest::FTruncateFileReturnError(const char *filename, off_t size) {
   auto fs = TestFS();
 
   int fd = OpenFile(fs.get(), filename);
-  return ::ftruncate(fd, size);
+  int retval = ::ftruncate(fd, size);
+  if (0 == retval) {
+    return 0;
+  } else {
+    return errno;
+  }
 }
 
 int FuseFTruncateTest::OpenFile(const TempTestFS *fs, const char *filename) {
diff --git a/src/test/fspp/fuse/ftruncate/testutils/FuseFTruncateTest.h b/src/test/fspp/fuse/ftruncate/testutils/FuseFTruncateTest.h
index b27cec5c..4942eab7 100644
--- a/src/test/fspp/fuse/ftruncate/testutils/FuseFTruncateTest.h
+++ b/src/test/fspp/fuse/ftruncate/testutils/FuseFTruncateTest.h
@@ -9,7 +9,7 @@ public:
   const char *FILENAME = "/myfile";
 
   void FTruncateFile(const char *filename, off_t size);
-  int FTruncateFileAllowError(const char *filename, off_t size);
+  int FTruncateFileReturnError(const char *filename, off_t size);
 
 private:
   int OpenFile(const TempTestFS *fs, const char *filename);
diff --git a/src/test/fspp/fuse/lstat/FuseLstatErrorTest.cpp b/src/test/fspp/fuse/lstat/FuseLstatErrorTest.cpp
index d2ba6b3c..d3cdca96 100644
--- a/src/test/fspp/fuse/lstat/FuseLstatErrorTest.cpp
+++ b/src/test/fspp/fuse/lstat/FuseLstatErrorTest.cpp
@@ -18,14 +18,12 @@ INSTANTIATE_TEST_CASE_P(LstatErrorCodes, FuseLstatErrorTest, Values(EACCES, EBAD
 TEST_F(FuseLstatErrorTest, ReturnNoError) {
   EXPECT_CALL(fsimpl, lstat(StrEq(FILENAME), _)).Times(1).WillOnce(ReturnIsFile);
   errno = 0;
-  int retval = LstatPathAllowErrors(FILENAME);
-  EXPECT_EQ(errno, 0);
-  EXPECT_EQ(retval, 0);
+  int error = LstatPathReturnError(FILENAME);
+  EXPECT_EQ(0, error);
 }
 
 TEST_P(FuseLstatErrorTest, ReturnError) {
   EXPECT_CALL(fsimpl, lstat(StrEq(FILENAME), _)).Times(1).WillOnce(Throw(FuseErrnoException(GetParam())));
-  int retval = LstatPathAllowErrors(FILENAME);
-  EXPECT_EQ(retval, -1);
-  EXPECT_EQ(GetParam(), errno);
+  int error = LstatPathReturnError(FILENAME);
+  EXPECT_EQ(GetParam(), error);
 }
diff --git a/src/test/fspp/fuse/lstat/testutils/FuseLstatTest.cpp b/src/test/fspp/fuse/lstat/testutils/FuseLstatTest.cpp
index d207726b..ebfda067 100644
--- a/src/test/fspp/fuse/lstat/testutils/FuseLstatTest.cpp
+++ b/src/test/fspp/fuse/lstat/testutils/FuseLstatTest.cpp
@@ -10,21 +10,26 @@ void FuseLstatTest::LstatPath(const std::string &path) {
   LstatPath(path, &dummy);
 }
 
-int FuseLstatTest::LstatPathAllowErrors(const std::string &path) {
+int FuseLstatTest::LstatPathReturnError(const std::string &path) {
   struct stat dummy;
-  return LstatPathAllowErrors(path, &dummy);
+  return LstatPathReturnError(path, &dummy);
 }
 
 void FuseLstatTest::LstatPath(const std::string &path, struct stat *result) {
-  int retval = LstatPathAllowErrors(path, result);
-  EXPECT_EQ(0, retval) << "lstat syscall failed. errno: " << errno;
+  int error = LstatPathReturnError(path, result);
+  EXPECT_EQ(0, error) << "lstat syscall failed. errno: " << error;
 }
 
-int FuseLstatTest::LstatPathAllowErrors(const std::string &path, struct stat *result) {
+int FuseLstatTest::LstatPathReturnError(const std::string &path, struct stat *result) {
   auto fs = TestFS();
 
   auto realpath = fs->mountDir() / path;
-  return ::lstat(realpath.c_str(), result);
+  int retval = ::lstat(realpath.c_str(), result);
+  if (retval == 0) {
+    return 0;
+  } else {
+    return errno;
+  }
 }
 
 struct stat FuseLstatTest::CallFileLstatWithImpl(function<void(struct stat*)> implementation) {
diff --git a/src/test/fspp/fuse/lstat/testutils/FuseLstatTest.h b/src/test/fspp/fuse/lstat/testutils/FuseLstatTest.h
index 961d56fb..04074dc2 100644
--- a/src/test/fspp/fuse/lstat/testutils/FuseLstatTest.h
+++ b/src/test/fspp/fuse/lstat/testutils/FuseLstatTest.h
@@ -22,9 +22,9 @@ protected:
   void LstatPath(const std::string &path, struct stat *result);
 
   // These two functions are the same as LstatPath above, but they don't fail the test when the lstat syscall
-  // crashes. Instead, they return the result value of the lstat syscall.
-  int LstatPathAllowErrors(const std::string &path);
-  int LstatPathAllowErrors(const std::string &path, struct stat *result);
+  // crashes. Instead, they return the value of errno after calling ::lstat.
+  int LstatPathReturnError(const std::string &path);
+  int LstatPathReturnError(const std::string &path, struct stat *result);
 
   // You can specify an implementation, which can modify the (struct stat *) result,
   // our fuse mock filesystem implementation will then return this to fuse on an lstat call.
diff --git a/src/test/fspp/fuse/mkdir/FuseMkdirErrorTest.cpp b/src/test/fspp/fuse/mkdir/FuseMkdirErrorTest.cpp
index 0e4d03a4..f4719737 100644
--- a/src/test/fspp/fuse/mkdir/FuseMkdirErrorTest.cpp
+++ b/src/test/fspp/fuse/mkdir/FuseMkdirErrorTest.cpp
@@ -16,12 +16,20 @@ class FuseMkdirErrorTest: public FuseMkdirTest, public WithParamInterface<int> {
 };
 INSTANTIATE_TEST_CASE_P(FuseMkdirErrorTest, FuseMkdirErrorTest, Values(EACCES, EDQUOT, EEXIST, EFAULT, ELOOP, EMLINK, ENAMETOOLONG, ENOENT, ENOMEM, ENOSPC, ENOTDIR, EPERM, EROFS, EBADF));
 
+TEST_F(FuseMkdirErrorTest, NoError) {
+  ReturnDoesntExistOnLstat(DIRNAME);
+  EXPECT_CALL(fsimpl, mkdir(StrEq(DIRNAME), _))
+    .Times(1).WillOnce(FromNowOnReturnIsDirOnLstat());
+
+  int error = MkdirReturnError(DIRNAME, 0);
+  EXPECT_EQ(0, error);
+}
+
 TEST_P(FuseMkdirErrorTest, ReturnedErrorIsCorrect) {
   ReturnDoesntExistOnLstat(DIRNAME);
   EXPECT_CALL(fsimpl, mkdir(StrEq(DIRNAME), _))
     .Times(1).WillOnce(Throw(FuseErrnoException(GetParam())));
 
-  int retval = MkdirAllowError(DIRNAME, 0);
-  EXPECT_EQ(GetParam(), errno);
-  EXPECT_EQ(-1, retval);
+  int error = MkdirReturnError(DIRNAME, 0);
+  EXPECT_EQ(GetParam(), error);
 }
diff --git a/src/test/fspp/fuse/mkdir/testutils/FuseMkdirTest.cpp b/src/test/fspp/fuse/mkdir/testutils/FuseMkdirTest.cpp
index a92e9cec..33044323 100644
--- a/src/test/fspp/fuse/mkdir/testutils/FuseMkdirTest.cpp
+++ b/src/test/fspp/fuse/mkdir/testutils/FuseMkdirTest.cpp
@@ -4,15 +4,20 @@ using ::testing::Action;
 using ::testing::Invoke;
 
 void FuseMkdirTest::Mkdir(const char *dirname, mode_t mode) {
-  int retval = MkdirAllowError(dirname, mode);
-  EXPECT_EQ(0, retval);
+  int error = MkdirReturnError(dirname, mode);
+  EXPECT_EQ(0, error);
 }
 
-int FuseMkdirTest::MkdirAllowError(const char *dirname, mode_t mode) {
+int FuseMkdirTest::MkdirReturnError(const char *dirname, mode_t mode) {
   auto fs = TestFS();
 
   auto realpath = fs->mountDir() / dirname;
-  return ::mkdir(realpath.c_str(), mode);
+  int retval = ::mkdir(realpath.c_str(), mode);
+  if (retval == 0) {
+    return 0;
+  } else {
+    return errno;
+  }
 }
 
 Action<void(const char*, mode_t)> FuseMkdirTest::FromNowOnReturnIsDirOnLstat() {
diff --git a/src/test/fspp/fuse/mkdir/testutils/FuseMkdirTest.h b/src/test/fspp/fuse/mkdir/testutils/FuseMkdirTest.h
index ec861a90..0baff266 100644
--- a/src/test/fspp/fuse/mkdir/testutils/FuseMkdirTest.h
+++ b/src/test/fspp/fuse/mkdir/testutils/FuseMkdirTest.h
@@ -9,7 +9,7 @@ public:
   const char *DIRNAME = "/mydir";
 
   void Mkdir(const char *dirname, mode_t mode);
-  int MkdirAllowError(const char *dirname, mode_t mode);
+  int MkdirReturnError(const char *dirname, mode_t mode);
 
   ::testing::Action<void(const char*, mode_t)> FromNowOnReturnIsDirOnLstat();
 };
diff --git a/src/test/fspp/fuse/openFile/FuseOpenErrorTest.cpp b/src/test/fspp/fuse/openFile/FuseOpenErrorTest.cpp
index 5829dec8..4ab7653a 100644
--- a/src/test/fspp/fuse/openFile/FuseOpenErrorTest.cpp
+++ b/src/test/fspp/fuse/openFile/FuseOpenErrorTest.cpp
@@ -13,21 +13,19 @@ using namespace fspp::fuse;
 
 class FuseOpenErrorTest: public FuseOpenTest, public WithParamInterface<int> {
 };
-INSTANTIATE_TEST_CASE_P(OpenErrorCodes, FuseOpenErrorTest, Values(EACCES, EDQUOT, EEXIST, EFAULT, EFBIG, EINTR, EOVERFLOW, EINVAL, EISDIR, ELOOP, EMFILE, ENAMETOOLONG, ENFILE, ENODEV, ENOENT, ENOMEM, ENOSPC, ENOTDIR, ENXIO, EOPNOTSUPP, EPERM, EROFS, ETXTBSY, EWOULDBLOCK, EBADF, ENOTDIR));
+INSTANTIATE_TEST_CASE_P(FuseOpenErrorTest, FuseOpenErrorTest, Values(EACCES, EDQUOT, EEXIST, EFAULT, EFBIG, EINTR, EOVERFLOW, EINVAL, EISDIR, ELOOP, EMFILE, ENAMETOOLONG, ENFILE, ENODEV, ENOENT, ENOMEM, ENOSPC, ENOTDIR, ENXIO, EOPNOTSUPP, EPERM, EROFS, ETXTBSY, EWOULDBLOCK, EBADF, ENOTDIR));
 
 TEST_F(FuseOpenErrorTest, ReturnNoError) {
   ReturnIsFileOnLstat(FILENAME);
   EXPECT_CALL(fsimpl, openFile(StrEq(FILENAME), _)).Times(1).WillOnce(Return(1));
   errno = 0;
-  int retval = OpenFileAllowError(FILENAME, O_RDONLY);
-  EXPECT_EQ(errno, 0);
-  EXPECT_GE(retval, 0);
+  int error = OpenFileReturnError(FILENAME, O_RDONLY);
+  EXPECT_EQ(0, error);
 }
 
 TEST_P(FuseOpenErrorTest, ReturnError) {
   ReturnIsFileOnLstat(FILENAME);
   EXPECT_CALL(fsimpl, openFile(StrEq(FILENAME), _)).Times(1).WillOnce(Throw(FuseErrnoException(GetParam())));
-  int retval = OpenFileAllowError(FILENAME, O_RDONLY);
-  EXPECT_EQ(retval, -1);
-  EXPECT_EQ(GetParam(), errno);
+  int error = OpenFileReturnError(FILENAME, O_RDONLY);
+  EXPECT_EQ(GetParam(), error);
 }
diff --git a/src/test/fspp/fuse/openFile/testutils/FuseOpenTest.cpp b/src/test/fspp/fuse/openFile/testutils/FuseOpenTest.cpp
index 176aaaf7..6a307b7f 100644
--- a/src/test/fspp/fuse/openFile/testutils/FuseOpenTest.cpp
+++ b/src/test/fspp/fuse/openFile/testutils/FuseOpenTest.cpp
@@ -6,9 +6,23 @@ int FuseOpenTest::OpenFile(const char *filename, int flags) {
   return fd;
 }
 
+int FuseOpenTest::OpenFileReturnError(const char *filename, int flags) {
+  int fd = OpenFileAllowError(filename, flags);
+  if (fd >= 0) {
+    return 0;
+  } else {
+    return -fd;
+  }
+}
+
 int FuseOpenTest::OpenFileAllowError(const char *filename, int flags) {
   auto fs = TestFS();
 
   auto realpath = fs->mountDir() / filename;
-  return ::open(realpath.c_str(), flags);
+  int fd = ::open(realpath.c_str(), flags);
+  if (fd >= 0) {
+    return fd;
+  } else {
+    return -errno;
+  }
 }
diff --git a/src/test/fspp/fuse/openFile/testutils/FuseOpenTest.h b/src/test/fspp/fuse/openFile/testutils/FuseOpenTest.h
index 943e9650..0d504985 100644
--- a/src/test/fspp/fuse/openFile/testutils/FuseOpenTest.h
+++ b/src/test/fspp/fuse/openFile/testutils/FuseOpenTest.h
@@ -9,6 +9,8 @@ public:
   const char *FILENAME = "/myfile";
 
   int OpenFile(const char *FILENAME, int flags);
+  int OpenFileReturnError(const char *FILENAME, int flags);
+private:
   int OpenFileAllowError(const char *FILENAME, int flags);
 };
 
diff --git a/src/test/fspp/fuse/read/FuseReadErrorTest.cpp b/src/test/fspp/fuse/read/FuseReadErrorTest.cpp
index 14d3d16f..07c6e0a2 100644
--- a/src/test/fspp/fuse/read/FuseReadErrorTest.cpp
+++ b/src/test/fspp/fuse/read/FuseReadErrorTest.cpp
@@ -33,10 +33,8 @@ TEST_P(FuseReadErrorTest, ReturnErrorOnFirstReadCall) {
     .WillRepeatedly(Throw(FuseErrnoException(GetParam())));
 
   char *buf = new char[READCOUNT];
-  errno = 0;
-  int retval = ReadFileAllowError(FILENAME, buf, READCOUNT, 0);
-  EXPECT_EQ(GetParam(), errno);
-  EXPECT_EQ(-1, retval);
+  auto retval = ReadFileReturnError(FILENAME, buf, READCOUNT, 0);
+  EXPECT_EQ(GetParam(), retval.error);
   delete[] buf;
 }
 
@@ -56,9 +54,8 @@ TEST_P(FuseReadErrorTest, ReturnErrorOnSecondReadCall) {
     .WillRepeatedly(Throw(FuseErrnoException(GetParam())));
 
   char *buf = new char[READCOUNT];
-  errno = 0;
-  size_t retval = ReadFileAllowError(FILENAME, buf, READCOUNT, 0);
-  EXPECT_EQ(0, errno);
-  EXPECT_EQ(successfullyReadBytes, retval); // Check that we're getting the number of successfully read bytes (the first read call) returned
+  auto retval = ReadFileReturnError(FILENAME, buf, READCOUNT, 0);
+  EXPECT_EQ(0, retval.error);
+  EXPECT_EQ(successfullyReadBytes, retval.read_bytes); // Check that we're getting the number of successfully read bytes (the first read call) returned
   delete[] buf;
 }
diff --git a/src/test/fspp/fuse/read/FuseReadOverflowTest.cpp b/src/test/fspp/fuse/read/FuseReadOverflowTest.cpp
index a1bf067e..78175d65 100644
--- a/src/test/fspp/fuse/read/FuseReadOverflowTest.cpp
+++ b/src/test/fspp/fuse/read/FuseReadOverflowTest.cpp
@@ -29,12 +29,12 @@ public:
 
 TEST_F(FuseReadOverflowTest, ReadMoreThanFileSizeFromBeginning) {
   char buf[READSIZE];
-  size_t read_bytes = ReadFileAllowError(FILENAME, buf, READSIZE, 0);
-  EXPECT_EQ(FILESIZE, read_bytes);
+  auto retval = ReadFileReturnError(FILENAME, buf, READSIZE, 0);
+  EXPECT_EQ(FILESIZE, retval.read_bytes);
 }
 
 TEST_F(FuseReadOverflowTest, ReadMoreThanFileSizeFromMiddle) {
   char buf[READSIZE];
-  size_t read_bytes = ReadFileAllowError(FILENAME, buf, READSIZE, OFFSET);
-  EXPECT_EQ(FILESIZE-OFFSET, read_bytes);
+  auto retval = ReadFileReturnError(FILENAME, buf, READSIZE, OFFSET);
+  EXPECT_EQ(FILESIZE-OFFSET, retval.read_bytes);
 }
diff --git a/src/test/fspp/fuse/read/testutils/FuseReadTest.cpp b/src/test/fspp/fuse/read/testutils/FuseReadTest.cpp
index 32c8e1ed..20345393 100644
--- a/src/test/fspp/fuse/read/testutils/FuseReadTest.cpp
+++ b/src/test/fspp/fuse/read/testutils/FuseReadTest.cpp
@@ -1,15 +1,21 @@
 #include "FuseReadTest.h"
 
 void FuseReadTest::ReadFile(const char *filename, void *buf, size_t count, off_t offset) {
-  size_t retval = ReadFileAllowError(filename, buf, count, offset);
-  EXPECT_EQ(count, retval);
+  auto retval = ReadFileReturnError(filename, buf, count, offset);
+  EXPECT_EQ(0, retval.error);
+  EXPECT_EQ(count, retval.read_bytes);
 }
 
-size_t FuseReadTest::ReadFileAllowError(const char *filename, void *buf, size_t count, off_t offset) {
+FuseReadTest::ReadError FuseReadTest::ReadFileReturnError(const char *filename, void *buf, size_t count, off_t offset) {
   auto fs = TestFS();
 
   int fd = OpenFile(fs.get(), filename);
-  return ::pread(fd, buf, count, offset);
+
+  ReadError result;
+  errno = 0;
+  result.read_bytes = ::pread(fd, buf, count, offset);
+  result.error = errno;
+  return result;
 }
 
 int FuseReadTest::OpenFile(const TempTestFS *fs, const char *filename) {
diff --git a/src/test/fspp/fuse/read/testutils/FuseReadTest.h b/src/test/fspp/fuse/read/testutils/FuseReadTest.h
index 45c0fa70..b5ce456c 100644
--- a/src/test/fspp/fuse/read/testutils/FuseReadTest.h
+++ b/src/test/fspp/fuse/read/testutils/FuseReadTest.h
@@ -8,8 +8,13 @@ class FuseReadTest: public FuseTest {
 public:
   const char *FILENAME = "/myfile";
 
+  struct ReadError {
+    int error;
+    size_t read_bytes;
+  };
+
   void ReadFile(const char *filename, void *buf, size_t count, off_t offset);
-  size_t ReadFileAllowError(const char *filename, void *buf, size_t count, off_t offset);
+  ReadError ReadFileReturnError(const char *filename, void *buf, size_t count, off_t offset);
 
   ::testing::Action<int(int, void*, size_t, off_t)> ReturnSuccessfulRead =
     ::testing::Invoke([](int, void *, size_t count, off_t) {
diff --git a/src/test/fspp/fuse/rename/FuseRenameErrorTest.cpp b/src/test/fspp/fuse/rename/FuseRenameErrorTest.cpp
index aacb0a69..9866fb7c 100644
--- a/src/test/fspp/fuse/rename/FuseRenameErrorTest.cpp
+++ b/src/test/fspp/fuse/rename/FuseRenameErrorTest.cpp
@@ -22,7 +22,6 @@ TEST_P(FuseRenameErrorTest, ReturnedErrorIsCorrect) {
   EXPECT_CALL(fsimpl, rename(StrEq(FILENAME1), StrEq(FILENAME2)))
     .Times(1).WillOnce(Throw(FuseErrnoException(GetParam())));
 
-  int retval = RenameAllowError(FILENAME1, FILENAME2);
-  EXPECT_EQ(GetParam(), errno);
-  EXPECT_EQ(-1, retval);
+  int error = RenameReturnError(FILENAME1, FILENAME2);
+  EXPECT_EQ(GetParam(), error);
 }
diff --git a/src/test/fspp/fuse/rename/testutils/FuseRenameTest.cpp b/src/test/fspp/fuse/rename/testutils/FuseRenameTest.cpp
index d3786fee..b0e1732c 100644
--- a/src/test/fspp/fuse/rename/testutils/FuseRenameTest.cpp
+++ b/src/test/fspp/fuse/rename/testutils/FuseRenameTest.cpp
@@ -4,14 +4,19 @@ using ::testing::Action;
 using ::testing::Invoke;
 
 void FuseRenameTest::Rename(const char *from, const char *to) {
-  int retval = RenameAllowError(from, to);
-  EXPECT_EQ(0, retval);
+  int error = RenameReturnError(from, to);
+  EXPECT_EQ(0, error);
 }
 
-int FuseRenameTest::RenameAllowError(const char *from, const char *to) {
+int FuseRenameTest::RenameReturnError(const char *from, const char *to) {
   auto fs = TestFS();
 
   auto realfrom = fs->mountDir() / from;
   auto realto = fs->mountDir() / to;
-  return ::rename(realfrom.c_str(), realto.c_str());
+  int retval = ::rename(realfrom.c_str(), realto.c_str());
+  if (0 == retval) {
+    return 0;
+  } else {
+    return errno;
+  }
 }
diff --git a/src/test/fspp/fuse/rename/testutils/FuseRenameTest.h b/src/test/fspp/fuse/rename/testutils/FuseRenameTest.h
index 2c86b40c..fe1366eb 100644
--- a/src/test/fspp/fuse/rename/testutils/FuseRenameTest.h
+++ b/src/test/fspp/fuse/rename/testutils/FuseRenameTest.h
@@ -10,7 +10,7 @@ public:
   const char *FILENAME2 = "/myfile2";
 
   void Rename(const char *from, const char *to);
-  int RenameAllowError(const char *from, const char *to);
+  int RenameReturnError(const char *from, const char *to);
 };
 
 #endif
diff --git a/src/test/fspp/fuse/rmdir/FuseRmdirErrorTest.cpp b/src/test/fspp/fuse/rmdir/FuseRmdirErrorTest.cpp
index 53f56c82..ac64f18d 100644
--- a/src/test/fspp/fuse/rmdir/FuseRmdirErrorTest.cpp
+++ b/src/test/fspp/fuse/rmdir/FuseRmdirErrorTest.cpp
@@ -21,7 +21,6 @@ TEST_P(FuseRmdirErrorTest, ReturnedErrorIsCorrect) {
   EXPECT_CALL(fsimpl, rmdir(StrEq(DIRNAME)))
     .Times(1).WillOnce(Throw(FuseErrnoException(GetParam())));
 
-  int retval = RmdirAllowError(DIRNAME);
-  EXPECT_EQ(GetParam(), errno);
-  EXPECT_EQ(-1, retval);
+  int error = RmdirReturnError(DIRNAME);
+  EXPECT_EQ(GetParam(), error);
 }
diff --git a/src/test/fspp/fuse/rmdir/testutils/FuseRmdirTest.cpp b/src/test/fspp/fuse/rmdir/testutils/FuseRmdirTest.cpp
index d59d1459..a655594c 100644
--- a/src/test/fspp/fuse/rmdir/testutils/FuseRmdirTest.cpp
+++ b/src/test/fspp/fuse/rmdir/testutils/FuseRmdirTest.cpp
@@ -4,15 +4,20 @@ using ::testing::Action;
 using ::testing::Invoke;
 
 void FuseRmdirTest::Rmdir(const char *dirname) {
-  int retval = RmdirAllowError(dirname);
-  EXPECT_EQ(0, retval);
+  int error = RmdirReturnError(dirname);
+  EXPECT_EQ(0, error);
 }
 
-int FuseRmdirTest::RmdirAllowError(const char *dirname) {
+int FuseRmdirTest::RmdirReturnError(const char *dirname) {
   auto fs = TestFS();
 
   auto realpath = fs->mountDir() / dirname;
-  return ::rmdir(realpath.c_str());
+  int retval = ::rmdir(realpath.c_str());
+  if (retval == 0) {
+    return 0;
+  } else {
+    return errno;
+  }
 }
 
 Action<void(const char*)> FuseRmdirTest::FromNowOnReturnDoesntExistOnLstat() {
diff --git a/src/test/fspp/fuse/rmdir/testutils/FuseRmdirTest.h b/src/test/fspp/fuse/rmdir/testutils/FuseRmdirTest.h
index ae156d25..90d9d69c 100644
--- a/src/test/fspp/fuse/rmdir/testutils/FuseRmdirTest.h
+++ b/src/test/fspp/fuse/rmdir/testutils/FuseRmdirTest.h
@@ -9,7 +9,7 @@ public:
   const char *DIRNAME = "/mydir";
 
   void Rmdir(const char *dirname);
-  int RmdirAllowError(const char *dirname);
+  int RmdirReturnError(const char *dirname);
 
   ::testing::Action<void(const char*)> FromNowOnReturnDoesntExistOnLstat();
 };
diff --git a/src/test/fspp/fuse/statfs/FuseStatfsErrorTest.cpp b/src/test/fspp/fuse/statfs/FuseStatfsErrorTest.cpp
index 9bae9797..44d24f4a 100644
--- a/src/test/fspp/fuse/statfs/FuseStatfsErrorTest.cpp
+++ b/src/test/fspp/fuse/statfs/FuseStatfsErrorTest.cpp
@@ -19,16 +19,13 @@ INSTANTIATE_TEST_CASE_P(FuseStatfsErrorTest, FuseStatfsErrorTest, Values(EACCES,
 TEST_F(FuseStatfsErrorTest, ReturnNoError) {
   ReturnIsFileOnLstat(FILENAME);
   EXPECT_CALL(fsimpl, statfs(StrEq(FILENAME), _)).Times(1).WillOnce(Return());
-  errno = 0;
-  int retval = StatfsAllowErrors(FILENAME);
-  EXPECT_EQ(errno, 0);
-  EXPECT_EQ(retval, 0);
+  int error = StatfsReturnError(FILENAME);
+  EXPECT_EQ(0, error);
 }
 
 TEST_P(FuseStatfsErrorTest, ReturnError) {
   ReturnIsFileOnLstat(FILENAME);
   EXPECT_CALL(fsimpl, statfs(StrEq(FILENAME), _)).Times(1).WillOnce(Throw(FuseErrnoException(GetParam())));
-  int retval = StatfsAllowErrors(FILENAME);
-  EXPECT_EQ(retval, -1);
-  EXPECT_EQ(GetParam(), errno);
+  int error = StatfsReturnError(FILENAME);
+  EXPECT_EQ(GetParam(), error);
 }
diff --git a/src/test/fspp/fuse/statfs/testutils/FuseStatfsTest.cpp b/src/test/fspp/fuse/statfs/testutils/FuseStatfsTest.cpp
index 13e6c599..7d0e09bd 100644
--- a/src/test/fspp/fuse/statfs/testutils/FuseStatfsTest.cpp
+++ b/src/test/fspp/fuse/statfs/testutils/FuseStatfsTest.cpp
@@ -10,21 +10,26 @@ void FuseStatfsTest::Statfs(const std::string &path) {
   Statfs(path, &dummy);
 }
 
-int FuseStatfsTest::StatfsAllowErrors(const std::string &path) {
+int FuseStatfsTest::StatfsReturnError(const std::string &path) {
   struct ::statvfs dummy;
-  return StatfsAllowErrors(path, &dummy);
+  return StatfsReturnError(path, &dummy);
 }
 
 void FuseStatfsTest::Statfs(const std::string &path, struct ::statvfs *result) {
-  int retval = StatfsAllowErrors(path, result);
-  EXPECT_EQ(0, retval) << "lstat syscall failed. errno: " << errno;
+  int error = StatfsReturnError(path, result);
+  EXPECT_EQ(0, error) << "lstat syscall failed. errno: " << errno;
 }
 
-int FuseStatfsTest::StatfsAllowErrors(const std::string &path, struct ::statvfs *result) {
+int FuseStatfsTest::StatfsReturnError(const std::string &path, struct ::statvfs *result) {
   auto fs = TestFS();
 
   auto realpath = fs->mountDir() / path;
-  return ::statvfs(realpath.c_str(), result);
+  int retval = ::statvfs(realpath.c_str(), result);
+  if (retval == 0) {
+    return 0;
+  } else {
+    return errno;
+  }
 }
 
 struct ::statvfs FuseStatfsTest::CallStatfsWithImpl(function<void(struct ::statvfs*)> implementation) {
diff --git a/src/test/fspp/fuse/statfs/testutils/FuseStatfsTest.h b/src/test/fspp/fuse/statfs/testutils/FuseStatfsTest.h
index 4f1a18a5..406c205f 100644
--- a/src/test/fspp/fuse/statfs/testutils/FuseStatfsTest.h
+++ b/src/test/fspp/fuse/statfs/testutils/FuseStatfsTest.h
@@ -23,8 +23,8 @@ protected:
 
   // These two functions are the same as Statfs above, but they don't fail the test when the statfs syscall
   // crashes. Instead, they return the result value of the statfs syscall.
-  int StatfsAllowErrors(const std::string &path);
-  int StatfsAllowErrors(const std::string &path, struct ::statvfs *result);
+  int StatfsReturnError(const std::string &path);
+  int StatfsReturnError(const std::string &path, struct ::statvfs *result);
 
   // You can specify an implementation, which can modify the (struct statfs *) result,
   // our fuse mock filesystem implementation will then return this to fuse on an statfs call.
diff --git a/src/test/fspp/fuse/truncate/FuseTruncateErrorTest.cpp b/src/test/fspp/fuse/truncate/FuseTruncateErrorTest.cpp
index 0daf39e2..67295eb4 100644
--- a/src/test/fspp/fuse/truncate/FuseTruncateErrorTest.cpp
+++ b/src/test/fspp/fuse/truncate/FuseTruncateErrorTest.cpp
@@ -21,7 +21,6 @@ TEST_P(FuseTruncateErrorTest, ReturnedErrorIsCorrect) {
   EXPECT_CALL(fsimpl, truncate(StrEq(FILENAME), _))
     .Times(1).WillOnce(Throw(FuseErrnoException(GetParam())));
 
-  int retval = TruncateFileAllowError(FILENAME, 0);
-  EXPECT_EQ(GetParam(), errno);
-  EXPECT_EQ(-1, retval);
+  int error = TruncateFileReturnError(FILENAME, 0);
+  EXPECT_EQ(GetParam(), error);
 }
diff --git a/src/test/fspp/fuse/truncate/testutils/FuseTruncateTest.cpp b/src/test/fspp/fuse/truncate/testutils/FuseTruncateTest.cpp
index d7753899..49516025 100644
--- a/src/test/fspp/fuse/truncate/testutils/FuseTruncateTest.cpp
+++ b/src/test/fspp/fuse/truncate/testutils/FuseTruncateTest.cpp
@@ -1,13 +1,18 @@
 #include "FuseTruncateTest.h"
 
 void FuseTruncateTest::TruncateFile(const char *filename, off_t size) {
-  int retval = TruncateFileAllowError(filename, size);
-  EXPECT_EQ(0, retval);
+  int error = TruncateFileReturnError(filename, size);
+  EXPECT_EQ(0, error);
 }
 
-int FuseTruncateTest::TruncateFileAllowError(const char *filename, off_t size) {
+int FuseTruncateTest::TruncateFileReturnError(const char *filename, off_t size) {
   auto fs = TestFS();
 
   auto realpath = fs->mountDir() / filename;
-  return ::truncate(realpath.c_str(), size);
+  int retval = ::truncate(realpath.c_str(), size);
+  if (retval == 0) {
+    return 0;
+  } else {
+    return errno;
+  }
 }
diff --git a/src/test/fspp/fuse/truncate/testutils/FuseTruncateTest.h b/src/test/fspp/fuse/truncate/testutils/FuseTruncateTest.h
index 33666846..9291cad0 100644
--- a/src/test/fspp/fuse/truncate/testutils/FuseTruncateTest.h
+++ b/src/test/fspp/fuse/truncate/testutils/FuseTruncateTest.h
@@ -9,7 +9,7 @@ public:
   const char *FILENAME = "/myfile";
 
   void TruncateFile(const char *filename, off_t size);
-  int TruncateFileAllowError(const char *filename, off_t size);
+  int TruncateFileReturnError(const char *filename, off_t size);
 };
 
 #endif
diff --git a/src/test/fspp/fuse/unlink/FuseUnlinkErrorTest.cpp b/src/test/fspp/fuse/unlink/FuseUnlinkErrorTest.cpp
index 60401835..f1a31514 100644
--- a/src/test/fspp/fuse/unlink/FuseUnlinkErrorTest.cpp
+++ b/src/test/fspp/fuse/unlink/FuseUnlinkErrorTest.cpp
@@ -21,7 +21,6 @@ TEST_P(FuseUnlinkErrorTest, ReturnedErrorIsCorrect) {
   EXPECT_CALL(fsimpl, unlink(StrEq(FILENAME)))
     .Times(1).WillOnce(Throw(FuseErrnoException(GetParam())));
 
-  int retval = UnlinkAllowError(FILENAME);
-  EXPECT_EQ(GetParam(), errno);
-  EXPECT_EQ(-1, retval);
+  int error = UnlinkReturnError(FILENAME);
+  EXPECT_EQ(GetParam(), error);
 }
diff --git a/src/test/fspp/fuse/unlink/testutils/FuseUnlinkTest.cpp b/src/test/fspp/fuse/unlink/testutils/FuseUnlinkTest.cpp
index 38bf93f7..37b990ae 100644
--- a/src/test/fspp/fuse/unlink/testutils/FuseUnlinkTest.cpp
+++ b/src/test/fspp/fuse/unlink/testutils/FuseUnlinkTest.cpp
@@ -4,15 +4,20 @@ using ::testing::Action;
 using ::testing::Invoke;
 
 void FuseUnlinkTest::Unlink(const char *filename) {
-  int retval = UnlinkAllowError(filename);
-  EXPECT_EQ(0, retval);
+  int error = UnlinkReturnError(filename);
+  EXPECT_EQ(0, error);
 }
 
-int FuseUnlinkTest::UnlinkAllowError(const char *filename) {
+int FuseUnlinkTest::UnlinkReturnError(const char *filename) {
   auto fs = TestFS();
 
   auto realpath = fs->mountDir() / filename;
-  return ::unlink(realpath.c_str());
+  int retval = ::unlink(realpath.c_str());
+  if (0 == retval) {
+    return 0;
+  } else {
+    return errno;
+  }
 }
 
 Action<void(const char*)> FuseUnlinkTest::FromNowOnReturnDoesntExistOnLstat() {
diff --git a/src/test/fspp/fuse/unlink/testutils/FuseUnlinkTest.h b/src/test/fspp/fuse/unlink/testutils/FuseUnlinkTest.h
index 9ca70b82..2e12b817 100644
--- a/src/test/fspp/fuse/unlink/testutils/FuseUnlinkTest.h
+++ b/src/test/fspp/fuse/unlink/testutils/FuseUnlinkTest.h
@@ -9,7 +9,7 @@ public:
   const char *FILENAME = "/myfile";
 
   void Unlink(const char *filename);
-  int UnlinkAllowError(const char *filename);
+  int UnlinkReturnError(const char *filename);
 
   ::testing::Action<void(const char*)> FromNowOnReturnDoesntExistOnLstat();
 };
diff --git a/src/test/fspp/fuse/utimens/FuseUtimensErrorTest.cpp b/src/test/fspp/fuse/utimens/FuseUtimensErrorTest.cpp
index 61128119..c8488bbf 100644
--- a/src/test/fspp/fuse/utimens/FuseUtimensErrorTest.cpp
+++ b/src/test/fspp/fuse/utimens/FuseUtimensErrorTest.cpp
@@ -21,7 +21,6 @@ TEST_P(FuseUtimensErrorTest, ReturnedErrorIsCorrect) {
   EXPECT_CALL(fsimpl, utimens(StrEq(FILENAME), _))
     .Times(1).WillOnce(Throw(FuseErrnoException(GetParam())));
 
-  int retval = UtimensAllowError(FILENAME, TIMEVALUES);
-  EXPECT_EQ(GetParam(), errno);
-  EXPECT_EQ(-1, retval);
+  int error = UtimensReturnError(FILENAME, TIMEVALUES);
+  EXPECT_EQ(GetParam(), error);
 }
diff --git a/src/test/fspp/fuse/utimens/testutils/FuseUtimensTest.cpp b/src/test/fspp/fuse/utimens/testutils/FuseUtimensTest.cpp
index 6bf32478..a4a0b9c6 100644
--- a/src/test/fspp/fuse/utimens/testutils/FuseUtimensTest.cpp
+++ b/src/test/fspp/fuse/utimens/testutils/FuseUtimensTest.cpp
@@ -4,11 +4,11 @@
 #include <sys/time.h>
 
 void FuseUtimensTest::Utimens(const char *filename, const timespec times[2]) {
-  int retval = UtimensAllowError(filename, times);
-  EXPECT_EQ(0, retval);
+  int error = UtimensReturnError(filename, times);
+  EXPECT_EQ(0, error);
 }
 
-int FuseUtimensTest::UtimensAllowError(const char *filename, const timespec times[2]) {
+int FuseUtimensTest::UtimensReturnError(const char *filename, const timespec times[2]) {
   auto fs = TestFS();
 
   auto realpath = fs->mountDir() / filename;
@@ -16,7 +16,12 @@ int FuseUtimensTest::UtimensAllowError(const char *filename, const timespec time
   struct timeval casted_times[2];
   TIMESPEC_TO_TIMEVAL(&casted_times[0], &times[0]);
   TIMESPEC_TO_TIMEVAL(&casted_times[1], &times[1]);
-  return ::utimes(realpath.c_str(), casted_times);
+  int retval = ::utimes(realpath.c_str(), casted_times);
+  if (0 == retval) {
+    return 0;
+  } else {
+    return errno;
+  }
 }
 
 struct timespec FuseUtimensTest::makeTimespec(time_t tv_sec, long tv_nsec) {
diff --git a/src/test/fspp/fuse/utimens/testutils/FuseUtimensTest.h b/src/test/fspp/fuse/utimens/testutils/FuseUtimensTest.h
index 4852d2d9..18285913 100644
--- a/src/test/fspp/fuse/utimens/testutils/FuseUtimensTest.h
+++ b/src/test/fspp/fuse/utimens/testutils/FuseUtimensTest.h
@@ -10,7 +10,7 @@ public:
   struct timespec TIMEVALUES[2] = {makeTimespec(0,0), makeTimespec(0,0)};
 
   void Utimens(const char *filename, const timespec times[2]);
-  int UtimensAllowError(const char *filename, const timespec times[2]);
+  int UtimensReturnError(const char *filename, const timespec times[2]);
 
   static struct timespec makeTimespec(time_t tv_sec, long tv_nsec);
 };
diff --git a/src/test/fspp/fuse/write/FuseWriteErrorTest.cpp b/src/test/fspp/fuse/write/FuseWriteErrorTest.cpp
index 41dca2c6..a6c31407 100644
--- a/src/test/fspp/fuse/write/FuseWriteErrorTest.cpp
+++ b/src/test/fspp/fuse/write/FuseWriteErrorTest.cpp
@@ -33,10 +33,8 @@ TEST_P(FuseWriteErrorTest, ReturnErrorOnFirstWriteCall) {
     .WillRepeatedly(Throw(FuseErrnoException(GetParam())));
 
   char *buf = new char[WRITECOUNT];
-  errno = 0;
-  int retval = WriteFileAllowError(FILENAME, buf, WRITECOUNT, 0);
-  EXPECT_EQ(GetParam(), errno);
-  EXPECT_EQ(-1, retval);
+  auto retval = WriteFileReturnError(FILENAME, buf, WRITECOUNT, 0);
+  EXPECT_EQ(GetParam(), retval.error);
   delete[] buf;
 }
 
@@ -55,10 +53,9 @@ TEST_P(FuseWriteErrorTest, ReturnErrorOnSecondWriteCall) {
     .WillRepeatedly(Throw(FuseErrnoException(GetParam())));
 
   char *buf = new char[WRITECOUNT];
-  errno = 0;
-  size_t retval = WriteFileAllowError(FILENAME, buf, WRITECOUNT, 0);
-  EXPECT_EQ(0, errno);
-  EXPECT_EQ(successfullyWrittenBytes, retval); // Check that we're getting the number of successfully written bytes (the first write call) returned
+  auto retval = WriteFileReturnError(FILENAME, buf, WRITECOUNT, 0);
+  EXPECT_EQ(0, retval.error);
+  EXPECT_EQ(successfullyWrittenBytes, retval.written_bytes); // Check that we're getting the number of successfully written bytes (the first write call) returned
   delete[] buf;
 }
 
diff --git a/src/test/fspp/fuse/write/testutils/FuseWriteTest.cpp b/src/test/fspp/fuse/write/testutils/FuseWriteTest.cpp
index 9fd51a57..9f464fdb 100644
--- a/src/test/fspp/fuse/write/testutils/FuseWriteTest.cpp
+++ b/src/test/fspp/fuse/write/testutils/FuseWriteTest.cpp
@@ -1,15 +1,21 @@
 #include "FuseWriteTest.h"
 
 void FuseWriteTest::WriteFile(const char *filename, const void *buf, size_t count, off_t offset) {
-  size_t retval = WriteFileAllowError(filename, buf, count, offset);
-  EXPECT_EQ(count, retval);
+  auto retval = WriteFileReturnError(filename, buf, count, offset);
+  EXPECT_EQ(0, retval.error);
+  EXPECT_EQ(count, retval.written_bytes);
 }
 
-size_t FuseWriteTest::WriteFileAllowError(const char *filename, const void *buf, size_t count, off_t offset) {
+FuseWriteTest::WriteError FuseWriteTest::WriteFileReturnError(const char *filename, const void *buf, size_t count, off_t offset) {
   auto fs = TestFS();
 
   int fd = OpenFile(fs.get(), filename);
-  return ::pwrite(fd, buf, count, offset);
+
+  WriteError result;
+  errno = 0;
+  result.written_bytes = ::pwrite(fd, buf, count, offset);
+  result.error = errno;
+  return result;
 }
 
 int FuseWriteTest::OpenFile(const TempTestFS *fs, const char *filename) {
diff --git a/src/test/fspp/fuse/write/testutils/FuseWriteTest.h b/src/test/fspp/fuse/write/testutils/FuseWriteTest.h
index 5430e682..65becf98 100644
--- a/src/test/fspp/fuse/write/testutils/FuseWriteTest.h
+++ b/src/test/fspp/fuse/write/testutils/FuseWriteTest.h
@@ -8,8 +8,13 @@ class FuseWriteTest: public FuseTest {
 public:
   const char *FILENAME = "/myfile";
 
+  struct WriteError {
+    int error;
+    size_t written_bytes;
+  };
+
   void WriteFile(const char *filename, const void *buf, size_t count, off_t offset);
-  size_t WriteFileAllowError(const char *filename, const void *buf, size_t count, off_t offset);
+  WriteError WriteFileReturnError(const char *filename, const void *buf, size_t count, off_t offset);
 
 private:
   int OpenFile(const TempTestFS *fs, const char *filename);