diff --git a/src/CBot/CBotFileUtils.cpp b/src/CBot/CBotFileUtils.cpp
index cdbc62af..cebe9acb 100644
--- a/src/CBot/CBotFileUtils.cpp
+++ b/src/CBot/CBotFileUtils.cpp
@@ -59,7 +59,7 @@ static bool ReadBinary(std::istream &istr, T &value)
     while (true)        // unsigned LEB128
     {
         if (!istr.read(reinterpret_cast<char*>(&chr), 1)) return false;
-        if (shift < sizeof(T) * 8 - 1)
+        if (shift < sizeof(T) * 8)
             value |= static_cast<T>(chr & 0x7F) << shift;
         shift += 7;
         if ((chr & 0x80) == 0) break;
diff --git a/test/unit/CBot/CBotFileUtils_test.cpp b/test/unit/CBot/CBotFileUtils_test.cpp
new file mode 100644
index 00000000..8f35118c
--- /dev/null
+++ b/test/unit/CBot/CBotFileUtils_test.cpp
@@ -0,0 +1,285 @@
+#include "CBot/CBotFileUtils.h"
+
+#include <gtest/gtest.h>
+
+namespace
+{
+std::string createTestStringWithAllPossibleCharacters()
+{
+    std::string testString;
+    for (char c = std::numeric_limits<char>::min(); ; ++c)
+    {
+        testString.push_back(c);
+        if (c == std::numeric_limits<char>::max()) break;
+    }
+    return testString;
+}
+}
+
+namespace CBot
+{
+
+struct CBotFileUtilsTest : public testing::Test
+{
+    std::stringstream stream;
+};
+
+struct CBotFileUtilsReadWriteByteTest : public CBotFileUtilsTest, public testing::WithParamInterface<char>
+{
+};
+
+TEST_P(CBotFileUtilsReadWriteByteTest, ReadByteValueShouldMatchWrittenValue)
+{
+    char expectedValue{GetParam()};
+    ASSERT_TRUE(WriteByte(stream, expectedValue));
+    char value{1};
+    ASSERT_TRUE(ReadByte(stream, value));
+    ASSERT_EQ(expectedValue, value);
+}
+
+INSTANTIATE_TEST_SUITE_P(
+    CBotIoReadWriteTest,
+    CBotFileUtilsReadWriteByteTest,
+    testing::Values(
+        '\0',
+        static_cast<char>(42),
+        std::numeric_limits<char>::min(),
+        std::numeric_limits<char>::max()));
+
+struct CBotFileUtilsReadWriteWordTest : public CBotFileUtilsTest, public testing::WithParamInterface<unsigned short>
+{
+};
+
+TEST_P(CBotFileUtilsReadWriteWordTest, ReadWordValueShouldMatchWrittenValue)
+{
+    unsigned short expectedValue{GetParam()};
+    ASSERT_TRUE(WriteWord(stream, expectedValue));
+    unsigned short value{1};
+    ASSERT_TRUE(ReadWord(stream, value));
+    ASSERT_EQ(expectedValue, value);
+}
+
+INSTANTIATE_TEST_SUITE_P(
+    CBotIoReadWriteTest,
+    CBotFileUtilsReadWriteWordTest,
+    testing::Values(
+        static_cast<unsigned short>(0),
+        static_cast<unsigned short>(42),
+        std::numeric_limits<unsigned short>::min(),
+        std::numeric_limits<unsigned short>::max() / 2,
+        std::numeric_limits<unsigned short>::max()));
+
+struct CBotFileUtilsReadWriteShortTest : public CBotFileUtilsTest, public testing::WithParamInterface<short>
+{
+};
+
+TEST_P(CBotFileUtilsReadWriteShortTest, ReadShortValueShouldMatchWrittenValue)
+{
+    short expectedValue{GetParam()};
+    ASSERT_TRUE(WriteShort(stream, expectedValue));
+    short value{1};
+    ASSERT_TRUE(ReadShort(stream, value));
+    ASSERT_EQ(expectedValue, value);
+}
+
+INSTANTIATE_TEST_SUITE_P(
+    CBotIoReadWriteTest,
+    CBotFileUtilsReadWriteShortTest,
+    testing::Values(
+        static_cast<short>(-7),
+        static_cast<short>(-1),
+        static_cast<short>(0),
+        static_cast<short>(42),
+        std::numeric_limits<short>::min(),
+        std::numeric_limits<short>::min() / 2,
+        std::numeric_limits<short>::max() / 2,
+        std::numeric_limits<short>::max()));
+
+struct CBotFileUtilsReadWriteUInt32Test : public CBotFileUtilsTest, public testing::WithParamInterface<uint32_t>
+{
+};
+
+TEST_P(CBotFileUtilsReadWriteUInt32Test, ReadUInt32ValueShouldMatchWrittenValue)
+{
+    uint32_t expectedValue{GetParam()};
+    ASSERT_TRUE(WriteUInt32(stream, expectedValue));
+    uint32_t value{1};
+    ASSERT_TRUE(ReadUInt32(stream, value));
+    ASSERT_EQ(expectedValue, value);
+}
+
+INSTANTIATE_TEST_SUITE_P(
+    CBotIoReadWriteTest,
+    CBotFileUtilsReadWriteUInt32Test,
+    testing::Values(
+        static_cast<uint32_t>(0),
+        static_cast<uint32_t>(42),
+        std::numeric_limits<uint32_t>::max() / 2,
+        std::numeric_limits<uint32_t>::max()));
+
+struct CBotFileUtilsReadWriteIntTest : public CBotFileUtilsTest, public testing::WithParamInterface<int>
+{
+};
+
+TEST_P(CBotFileUtilsReadWriteIntTest, ReadIntValueShouldMatchWrittenValue)
+{
+    int expectedValue{GetParam()};
+    ASSERT_TRUE(WriteInt(stream, expectedValue));
+    int value{1};
+    ASSERT_TRUE(ReadInt(stream, value));
+    ASSERT_EQ(expectedValue, value);
+}
+
+INSTANTIATE_TEST_SUITE_P(
+    CBotIoReadWriteTest,
+    CBotFileUtilsReadWriteIntTest,
+    testing::Values(
+        static_cast<int>(7),
+        static_cast<int>(-1),
+        static_cast<int>(0),
+        static_cast<int>(42),
+        std::numeric_limits<int>::min(),
+        std::numeric_limits<int>::min() / 2,
+        std::numeric_limits<int>::max() / 2,
+        std::numeric_limits<int>::max()));
+
+struct CBotFileUtilsReadWriteLongTest : public CBotFileUtilsTest, public testing::WithParamInterface<long>
+{
+};
+
+TEST_P(CBotFileUtilsReadWriteLongTest, ReadLongValueShouldMatchWrittenValue)
+{
+    long value{1};
+    long expectedValue{GetParam()};
+    ASSERT_TRUE(WriteLong(stream, expectedValue));
+    ASSERT_TRUE(ReadLong(stream, value));
+    ASSERT_EQ(expectedValue, value);
+}
+
+TEST_P(CBotFileUtilsReadWriteLongTest, ReadLongValueShouldMatchWrittenValueWithPadding)
+{
+    constexpr int padding = 10;
+    long expectedValue{GetParam()};
+    ASSERT_TRUE(WriteLong(stream, expectedValue, padding));
+    long value{1};
+    ASSERT_TRUE(ReadLong(stream, value));
+    ASSERT_EQ(expectedValue, value);
+}
+
+TEST_P(CBotFileUtilsReadWriteLongTest, ReadLongValueShouldMatchWrittenValueWithPaddingAndMultipleValues)
+{
+    constexpr int padding = 10;
+    long value{1};
+    long expectedValue{GetParam()};
+    int anotherValue{1};
+    int anotherExpectedValue{2};
+    ASSERT_TRUE(WriteLong(stream, expectedValue, padding));
+    ASSERT_TRUE(WriteInt(stream, anotherExpectedValue));
+    ASSERT_TRUE(ReadLong(stream, value));
+    ASSERT_TRUE(ReadInt(stream, anotherValue));
+    ASSERT_EQ(expectedValue, value);
+    ASSERT_EQ(anotherExpectedValue, anotherValue);
+}
+
+INSTANTIATE_TEST_SUITE_P(
+    CBotIoReadWriteTest,
+    CBotFileUtilsReadWriteLongTest,
+    testing::Values(
+        static_cast<long>(7),
+        static_cast<long>(-1),
+        static_cast<long>(0),
+        static_cast<long>(42),
+        std::numeric_limits<long>::min(),
+        std::numeric_limits<long>::min() / 2,
+        std::numeric_limits<long>::max() / 2,
+        std::numeric_limits<long>::max()));
+
+struct CBotFileUtilsReadWriteFloatTest : public CBotFileUtilsTest, public testing::WithParamInterface<float>
+{
+};
+
+TEST_P(CBotFileUtilsReadWriteFloatTest, ReadFloatValueShouldMatchWrittenValue)
+{
+    float expectedValue{GetParam()};
+    ASSERT_TRUE(WriteFloat(stream, expectedValue));
+    float value{1.0f};
+    ASSERT_TRUE(ReadFloat(stream, value));
+    ASSERT_EQ(expectedValue, value);
+}
+
+INSTANTIATE_TEST_SUITE_P(
+    CBotIoReadWriteTest,
+    CBotFileUtilsReadWriteFloatTest,
+    testing::Values(
+        7.0f,
+        -1.0f,
+        0.0f,
+        42.0f,
+        3.14f,
+        -2.73f,
+        std::numeric_limits<float>::min(),
+        std::numeric_limits<float>::min() / 2.0f,
+        std::numeric_limits<float>::max() / 2.0f,
+        std::numeric_limits<float>::max()));
+
+struct CBotFileUtilsReadWriteDoubleTest : public CBotFileUtilsTest, public testing::WithParamInterface<double>
+{
+};
+
+TEST_P(CBotFileUtilsReadWriteDoubleTest, ReadDoubleValueShouldMatchWrittenValue)
+{
+    double expectedValue{GetParam()};
+    ASSERT_TRUE(WriteDouble(stream, expectedValue));
+    double value{1.0};
+    ASSERT_TRUE(ReadDouble(stream, value));
+    ASSERT_EQ(expectedValue, value);
+}
+
+INSTANTIATE_TEST_SUITE_P(
+    CBotIoReadWriteTest,
+    CBotFileUtilsReadWriteDoubleTest,
+    testing::Values(
+        7.0,
+        -1.0,
+        0.0,
+        42.0,
+        3.14,
+        -2.73,
+        std::numeric_limits<double>::min(),
+        std::numeric_limits<double>::min() / 2.0,
+        std::numeric_limits<double>::max() / 2.0,
+        std::numeric_limits<double>::max()));
+
+struct CBotFileUtilsReadWriteStringTest : public CBotFileUtilsTest, public testing::WithParamInterface<std::string>
+{
+};
+
+TEST_P(CBotFileUtilsReadWriteStringTest, ReadStringValueShouldMatchWrittenValue)
+{
+    std::string expectedValue{GetParam()};
+    ASSERT_TRUE(WriteString(stream, expectedValue));
+    std::string value{"test"};
+    ASSERT_TRUE(ReadString(stream, value));
+    ASSERT_EQ(expectedValue, value);
+}
+
+INSTANTIATE_TEST_SUITE_P(
+    CBotIoReadWriteTest,
+    CBotFileUtilsReadWriteStringTest,
+    testing::Values(
+        "",
+        "123",
+        "abc",
+        createTestStringWithAllPossibleCharacters()));
+
+TEST_F(CBotFileUtilsTest, ReadStreamShouldMatchWrittenStream)
+{
+    std::string expectedValue{"Lorem ipsum dolor sit amet"};
+    std::stringstream initialStream{expectedValue};
+    ASSERT_TRUE(WriteStream(stream, initialStream));
+    std::stringstream newStream{};
+    ASSERT_TRUE(ReadStream(stream, newStream));
+    ASSERT_EQ(expectedValue, newStream.str());
+}
+
+}
diff --git a/test/unit/CBot/CBot_test.cpp b/test/unit/CBot/CBot_test.cpp
index 3d1ee516..7da15f69 100644
--- a/test/unit/CBot/CBot_test.cpp
+++ b/test/unit/CBot/CBot_test.cpp
@@ -320,200 +320,6 @@ protected:
     }
 };
 
-TEST_F(CBotUT, TestSaveStateIOFunctions)
-{
-    std::stringstream sstr("");
-    std::string teststring;
-
-    for (char c = std::numeric_limits<char>::min() ;; ++c)
-    {
-        teststring.push_back(c);
-        if ( c == std::numeric_limits<char>::max() ) break;
-    }
-
-    auto CallWriteFunctions = [&sstr, &teststring]() -> bool
-    {
-        if (!WriteWord(sstr, static_cast<unsigned short>(0))) return false;
-        if (!WriteWord(sstr, std::numeric_limits<unsigned short>::max() / 2)) return false;
-        if (!WriteWord(sstr, std::numeric_limits<unsigned short>::max())) return false;
-
-        if (!WriteByte(sstr, std::numeric_limits<char>::min())) return false;
-        if (!WriteByte(sstr, std::numeric_limits<char>::max())) return false;
-
-        if (!WriteShort(sstr, std::numeric_limits<short>::min())) return false;
-        if (!WriteShort(sstr, std::numeric_limits<short>::min() / 2)) return false;
-        if (!WriteShort(sstr, -1)) return false;
-        if (!WriteShort(sstr, 0)) return false;
-        if (!WriteShort(sstr, std::numeric_limits<short>::max() / 2)) return false;
-        if (!WriteShort(sstr, std::numeric_limits<short>::max())) return false;
-
-        if (!WriteUInt32(sstr, static_cast<uint32_t>(0))) return false;
-        if (!WriteUInt32(sstr, std::numeric_limits<uint32_t>::max() / 2)) return false;
-        if (!WriteUInt32(sstr, std::numeric_limits<uint32_t>::max())) return false;
-
-        if (!WriteInt(sstr, std::numeric_limits<int>::min())) return false;
-        if (!WriteInt(sstr, std::numeric_limits<int>::min() / 2)) return false;
-        if (!WriteInt(sstr, -1)) return false;
-        if (!WriteInt(sstr, 0)) return false;
-        if (!WriteInt(sstr, std::numeric_limits<int>::max() / 2)) return false;
-        if (!WriteInt(sstr, std::numeric_limits<int>::max())) return false;
-
-        if (!WriteLong(sstr, std::numeric_limits<long>::min())) return false;
-        if (!WriteLong(sstr, std::numeric_limits<long>::min() / 2L)) return false;
-        if (!WriteLong(sstr, -1L)) return false;
-        if (!WriteLong(sstr, 0L)) return false;
-        if (!WriteLong(sstr, std::numeric_limits<long>::max() / 2L)) return false;
-        if (!WriteLong(sstr, std::numeric_limits<long>::max())) return false;
-
-        // test with padding bytes (not currently used anywhere)
-        if (!WriteLong(sstr, 1234567890L, 10)) return false;
-
-        if (!WriteFloat(sstr, std::numeric_limits<float>::min())) return false;
-        if (!WriteFloat(sstr, 0.0f)) return false;
-        if (!WriteFloat(sstr, std::numeric_limits<float>::max())) return false;
-
-        if (!WriteDouble(sstr, std::numeric_limits<double>::min())) return false;
-        if (!WriteDouble(sstr, 0.0)) return false;
-        if (!WriteDouble(sstr, std::numeric_limits<double>::max())) return false;
-
-        if (!WriteString(sstr, "")) return false;
-        if (!WriteString(sstr, teststring)) return false;
-        return true;
-    };
-
-    if ( !CallWriteFunctions() )
-    {
-        ADD_FAILURE() << "failed in CallWriteFunctions()" << std::endl;
-        return;
-    }
-
-    std::stringstream savestream("");
-
-    if ( !WriteStream(savestream, sstr) )
-    {
-        ADD_FAILURE() << "CBot::WriteStream() failed" << std::endl;
-        return;
-    }
-
-    std::stringstream newstream("");
-
-    if ( !ReadStream(savestream, newstream) )
-    {
-        ADD_FAILURE() << "CBot:ReadStream() failed" << std::endl;
-        return;
-    }
-
-    auto CallReadFunctions = [&teststring, &newstream]() -> bool
-    {
-        unsigned short w = 1;
-        if (!ReadWord(newstream, w)) return false;
-        if (w != static_cast<unsigned short>(0)) return false;
-        if (!ReadWord(newstream, w)) return false;
-        if (w != std::numeric_limits<unsigned short>::max() / 2) return false;
-
-        if (!ReadWord(newstream, w)) return false;
-        if (w != std::numeric_limits<unsigned short>::max()) return false;
-
-        char c = 1;
-        if (!ReadByte(newstream, c)) return false;
-        if (c != std::numeric_limits<char>::min()) return false;
-        if (!ReadByte(newstream, c)) return false;
-        if (c != std::numeric_limits<char>::max()) return false;
-
-        short s = 1;
-        if (!ReadShort(newstream, s)) return false;
-        if (s != std::numeric_limits<short>::min()) return false;
-        if (!ReadShort(newstream, s)) return false;
-        if (s != std::numeric_limits<short>::min() / 2) return false;
-
-        if (!ReadShort(newstream, s)) return false;
-        if (s != -1) return false;
-        if (!ReadShort(newstream, s)) return false;
-        if (s != 0) return false;
-
-        if (!ReadShort(newstream, s)) return false;
-        if (s != std::numeric_limits<short>::max() / 2) return false;
-        if (!ReadShort(newstream, s)) return false;
-        if (s != std::numeric_limits<short>::max()) return false;
-
-        uint32_t u = 1;
-        if (!ReadUInt32(newstream, u)) return false;
-        if (u != static_cast<uint32_t>(0)) return false;
-        if (!ReadUInt32(newstream, u)) return false;
-        if (u != std::numeric_limits<uint32_t>::max() / 2) return false;
-
-        if (!ReadUInt32(newstream, u)) return false;
-        if (u != std::numeric_limits<uint32_t>::max()) return false;
-
-        int i = 1;
-        if (!ReadInt(newstream, i)) return false;
-        if (i != std::numeric_limits<int>::min()) return false;
-        if (!ReadInt(newstream, i)) return false;
-        if (i != std::numeric_limits<int>::min() / 2) return false;
-
-        if (!ReadInt(newstream, i)) return false;
-        if (i != -1) return false;
-        if (!ReadInt(newstream, i)) return false;
-        if (i != 0) return false;
-
-        if (!ReadInt(newstream, i)) return false;
-        if (i != std::numeric_limits<int>::max() / 2) return false;
-        if (!ReadInt(newstream, i)) return false;
-        if (i != std::numeric_limits<int>::max()) return false;
-
-        long l = 1L;
-        if (!ReadLong(newstream, l)) return false;
-        if (l != std::numeric_limits<long>::min()) return false;
-        if (!ReadLong(newstream, l)) return false;
-        if (l != std::numeric_limits<long>::min() / 2L) return false;
-
-        if (!ReadLong(newstream, l)) return false;
-        if (l != -1L) return false;
-        if (!ReadLong(newstream, l)) return false;
-        if (l != 0L) return false;
-
-        if (!ReadLong(newstream, l)) return false;
-        if (l != std::numeric_limits<long>::max() / 2L) return false;
-        if (!ReadLong(newstream, l)) return false;
-        if (l != std::numeric_limits<long>::max()) return false;
-
-        if (!ReadLong(newstream, l)) return false;
-        if (l != 1234567890L) return false;
-
-        float f = 1.0f;
-        if (!ReadFloat(newstream, f)) return false;
-        if (f != std::numeric_limits<float>::min()) return false;
-        if (!ReadFloat(newstream, f)) return false;
-        if (f != 0.0f) return false;
-
-        if (!ReadFloat(newstream, f)) return false;
-        if (f != std::numeric_limits<float>::max()) return false;
-
-        double d = 1.0;
-        if (!ReadDouble(newstream, d)) return false;
-        if (d != std::numeric_limits<double>::min()) return false;
-        if (!ReadDouble(newstream, d)) return false;
-        if (d != 0.0) return false;
-
-        if (!ReadDouble(newstream, d)) return false;
-        if (d != std::numeric_limits<double>::max()) return false;
-
-        std::string newstring = "should be empty string after next read";
-        if (!ReadString(newstream, newstring)) return false;
-        if (newstring != "") return false;
-
-        if (!ReadString(newstream, newstring)) return false;
-        if (newstring != teststring) return false;
-        return true;
-    };
-
-    if ( !CallReadFunctions() )
-    {
-        ADD_FAILURE() << "failed in CallReadFunctions()" << std::endl;
-        return;
-    }
-}
-
 TEST_F(CBotUT, EmptyTest)
 {
     ExecuteTest(
diff --git a/test/unit/CMakeLists.txt b/test/unit/CMakeLists.txt
index b549229e..8eb7d7a5 100644
--- a/test/unit/CMakeLists.txt
+++ b/test/unit/CMakeLists.txt
@@ -11,8 +11,9 @@ add_definitions(-DGTEST_HAS_TR1_TUPLE=0)
 add_executable(colobot_ut
     main.cpp
     app/app_test.cpp
-    CBot/CBotToken_test.cpp
     CBot/CBot_test.cpp
+    CBot/CBotFileUtils_test.cpp
+    CBot/CBotToken_test.cpp
     common/config_file_test.cpp
     common/timeutils_test.cpp
     graphics/engine/lightman_test.cpp