diff --git a/test/sys_file_unittest.cpp b/test/sys_file_unittest.cpp
new file mode 100644
index 0000000..f4035cf
--- /dev/null
+++ b/test/sys_file_unittest.cpp
@@ -0,0 +1,131 @@
+#include "sys_file.hpp"
+#include "sys_mock.hpp"
+
+#include <fcntl.h>
+
+#include <cstring>
+#include <memory>
+
+#include <gmock/gmock.h>
+
+using namespace binstore;
+using namespace std::string_literals;
+
+using ::testing::_;
+using ::testing::Args;
+using ::testing::Ge;
+using ::testing::IsEmpty;
+using ::testing::NotNull;
+using ::testing::Return;
+using ::testing::SetErrnoAndReturn;
+using ::testing::StrEq;
+using ::testing::WithArgs;
+
+static constexpr int sysFileTestFd = 42;
+static inline std::string sysFileTestPath = "/test/path"s;
+static constexpr size_t sysFileTestOffset = 0;
+auto static const sysFileTestStr = "Hello, \0+.world!\0"s;
+std::vector<uint8_t> static const sysFileTestBuf(sysFileTestStr.begin(),
+                                                 sysFileTestStr.end());
+
+class SysFileTest : public ::testing::Test
+{
+  protected:
+    SysFileTest()
+    {
+        EXPECT_CALL(sys, open(StrEq(sysFileTestPath), O_RDWR))
+            .WillOnce(Return(sysFileTestFd));
+        EXPECT_CALL(sys, close(sysFileTestFd));
+
+        file = std::make_unique<SysFileImpl>(sysFileTestPath, sysFileTestOffset,
+                                             &sys);
+    }
+
+    const internal::SysMock sys;
+
+    std::unique_ptr<SysFile> file;
+};
+
+ACTION_P(BufSet, buf)
+{
+    size_t count = std::min(arg1, buf.size());
+    std::memcpy(arg0, buf.data(), count);
+
+    return count;
+}
+
+ACTION_P2(BufSetAndGetStartAddr, buf, addrPtr)
+{
+    size_t count = std::min(arg1, buf.size());
+    std::memcpy(arg0, buf.data(), count);
+    *addrPtr = arg0;
+
+    return count;
+}
+
+ACTION_P2(BufSetTruncated, buf, offset)
+{
+    size_t count = std::min(arg1, buf.size() - offset);
+    std::memcpy(arg0, buf.data() + offset, count);
+
+    return count;
+}
+
+TEST_F(SysFileTest, ReadSucceeds)
+{
+    EXPECT_CALL(sys, lseek(sysFileTestFd, 0, SEEK_SET));
+    EXPECT_CALL(sys, read(sysFileTestFd, NotNull(), _))
+        .WillOnce(WithArgs<1, 2>(BufSet(sysFileTestBuf)));
+
+    EXPECT_EQ(sysFileTestStr, file->readAsStr(0, sysFileTestBuf.size()));
+}
+
+TEST_F(SysFileTest, ReadMoreThanAvailable)
+{
+    EXPECT_CALL(sys, lseek(sysFileTestFd, 0, SEEK_SET));
+    EXPECT_CALL(sys, read(sysFileTestFd, NotNull(), _))
+        .WillOnce(WithArgs<1, 2>(BufSet(sysFileTestBuf)))
+        .WillOnce(Return(0));
+
+    EXPECT_EQ(sysFileTestStr, file->readAsStr(0, sysFileTestBuf.size() + 1024));
+}
+
+TEST_F(SysFileTest, ReadAtOffset)
+{
+    const size_t testOffset = 2;
+    std::string truncBuf = sysFileTestStr.substr(testOffset);
+
+    EXPECT_CALL(sys, lseek(sysFileTestFd, testOffset, SEEK_SET));
+    EXPECT_CALL(sys, read(sysFileTestFd, NotNull(), _))
+        .WillOnce(WithArgs<1, 2>(BufSetTruncated(sysFileTestBuf, testOffset)));
+
+    EXPECT_EQ(truncBuf, file->readAsStr(testOffset, truncBuf.size()));
+}
+
+TEST_F(SysFileTest, ReadRemainingFail)
+{
+    EXPECT_CALL(sys, lseek(sysFileTestFd, 0, SEEK_SET));
+    EXPECT_CALL(sys, read(sysFileTestFd, NotNull(), _))
+        .WillOnce(SetErrnoAndReturn(EIO, -1));
+
+    EXPECT_THROW(file->readRemainingAsStr(0), std::exception);
+}
+
+TEST_F(SysFileTest, ReadRemainingSucceeds)
+{
+    EXPECT_CALL(sys, lseek(sysFileTestFd, 0, SEEK_SET));
+    EXPECT_CALL(sys, read(sysFileTestFd, NotNull(), _))
+        .WillOnce(WithArgs<1, 2>(BufSet(sysFileTestBuf)))
+        .WillOnce(Return(0)); // EOF
+
+    EXPECT_EQ(sysFileTestStr, file->readRemainingAsStr(0));
+}
+
+TEST_F(SysFileTest, ReadRemainingBeyondEndReturnsEmpty)
+{
+    const size_t largeOffset = 9000;
+    EXPECT_CALL(sys, lseek(sysFileTestFd, largeOffset, SEEK_SET));
+    EXPECT_CALL(sys, read(sysFileTestFd, NotNull(), _)).WillOnce(Return(0));
+
+    EXPECT_THAT(file->readRemainingAsStr(largeOffset), IsEmpty());
+}