diff --git a/src/test/cli_argument_parser.cpp b/src/test/cli_argument_parser.cpp
index 769d6a5..5979778 100644
--- a/src/test/cli_argument_parser.cpp
+++ b/src/test/cli_argument_parser.cpp
@@ -148,6 +148,7 @@ int main(int argc, char* argv[]) {
     ASSERT(!validTestParameterParser.getUnpositionalArgument('z').isError);
     ASSERT(validTestParameterParser.getUnpositionalArgument('z').errorCode == ErrorCodes::NOT_PRESENT);
     ASSERT(validTestParameterParser.getUnpositionalArgument('z').value == std::string(""));
+    ASSERT(validTestParameterParser.wrongUsageMessages.size() == 0);
 
     delete[] validTestParameterList;
     std::cout << "Passed valid input test." << std::endl;
@@ -170,6 +171,7 @@ int main(int argc, char* argv[]) {
     CLI::ArgumentsParser validEmptyTestParameterParser = CLI::ArgumentsParser(emptyTestParameterCount, emptyTestParameterList, emptyTestFlags, emptyTestUnpositionalArguments, emptyTestPositionalArguments);
     ASSERT(!validEmptyTestParameterParser.wrongUsage);
     ASSERT(validEmptyTestParameterParser.programName == std::string("test"));
+    ASSERT(validEmptyTestParameterParser.wrongUsageMessages.size() == 0);
 
     //invalid
     emptyTestPositionalArguments.push_back(CLI::PositionalArgument("argument", "positional argument"));
@@ -179,6 +181,8 @@ int main(int argc, char* argv[]) {
     ASSERT(invalidEmptyTestParameterParser.programName == std::string("test"));
     ASSERT(invalidEmptyTestParameterParser.getPositionalArgument(0).isError);
     ASSERT(invalidEmptyTestParameterParser.getPositionalArgument(0).errorCode == ErrorCodes::NOT_PRESENT);
+    ASSERT(invalidEmptyTestParameterParser.wrongUsageMessages.size() == 1);
+    ASSERT(invalidEmptyTestParameterParser.wrongUsageMessages.at(0) == "Too few positional arguments! Missing: argument");
 
     delete[] emptyTestParameterList;
     std::cout << "Passed empty input test." << std::endl;
@@ -214,6 +218,8 @@ int main(int argc, char* argv[]) {
     ASSERT(unknownFlagStandaloneTestParser.getFlag(std::string("four")).isError);
     ASSERT(unknownFlagStandaloneTestParser.getFlag(std::string("four")).errorCode == ErrorCodes::NOT_PRESENT);
     ASSERT(!unknownFlagStandaloneTestParser.getFlag(std::string("four")).value);
+    ASSERT(unknownFlagStandaloneTestParser.wrongUsageMessages.size() == 1);
+    ASSERT(unknownFlagStandaloneTestParser.wrongUsageMessages.at(0) == "Unknown argument or flag(s): a");
 
     int unknownFlagMixedTestParameterCount = 7;
 
@@ -224,6 +230,8 @@ int main(int argc, char* argv[]) {
     ASSERT(unknownFlagMixedTestParser.getFlag(std::string("four")).isError);
     ASSERT(unknownFlagMixedTestParser.getFlag(std::string("four")).errorCode == ErrorCodes::WRONG_USAGE);
     ASSERT(unknownFlagMixedTestParser.getFlag(std::string("four")).value);
+    ASSERT(unknownFlagMixedTestParser.wrongUsageMessages.size() == 1);
+    ASSERT(unknownFlagMixedTestParser.wrongUsageMessages.at(0) == "Unknown argument or flag(s): a");
 
     delete[] unknownFlagTestParameterList;
 
@@ -256,6 +264,8 @@ int main(int argc, char* argv[]) {
     ASSERT(unknownLongFlagStandaloneTestParser.getFlag(std::string("four")).isError);
     ASSERT(unknownLongFlagStandaloneTestParser.getFlag(std::string("four")).errorCode == ErrorCodes::NOT_PRESENT);
     ASSERT(!unknownLongFlagStandaloneTestParser.getFlag(std::string("four")).value);
+    ASSERT(unknownLongFlagStandaloneTestParser.wrongUsageMessages.size() == 1);
+    ASSERT(unknownLongFlagStandaloneTestParser.wrongUsageMessages.at(0) == "Unknown argument or flag: --a");
 
     int unknownLongFlagMixedTestParameterCount = 7;
 
@@ -266,6 +276,8 @@ int main(int argc, char* argv[]) {
     ASSERT(unknownLongFlagMixedTestParser.getFlag(std::string("four")).isError);
     ASSERT(unknownLongFlagMixedTestParser.getFlag(std::string("four")).errorCode == ErrorCodes::WRONG_USAGE);
     ASSERT(unknownLongFlagMixedTestParser.getFlag(std::string("four")).value);
+    ASSERT(unknownLongFlagMixedTestParser.wrongUsageMessages.size() == 1);
+    ASSERT(unknownLongFlagMixedTestParser.wrongUsageMessages.at(0) == "Unknown argument or flag: --a");
 
     delete[] unknownLongFlagTestParameterList;
     std::cout << "Passed unknown flag test." << std::endl;
@@ -301,6 +313,8 @@ int main(int argc, char* argv[]) {
     ASSERT(unknownArgumentStandaloneTestParser.getUnpositionalArgument(std::string("four")).isError);
     ASSERT(unknownArgumentStandaloneTestParser.getUnpositionalArgument(std::string("four")).errorCode == ErrorCodes::NOT_PRESENT);
     ASSERT(unknownArgumentStandaloneTestParser.getUnpositionalArgument(std::string("four")).value == "");
+    ASSERT(unknownArgumentStandaloneTestParser.wrongUsageMessages.size() == 1);
+    ASSERT(unknownArgumentStandaloneTestParser.wrongUsageMessages.at(0) == "Unknown argument or flag(s): a123");
 
     int unknownArgumentMixedTestParameterCount = 7;
 
@@ -311,6 +325,8 @@ int main(int argc, char* argv[]) {
     ASSERT(unknownArgumentMixedTestParser.getUnpositionalArgument(std::string("four")).isError);
     ASSERT(unknownArgumentMixedTestParser.getUnpositionalArgument(std::string("four")).errorCode == ErrorCodes::WRONG_USAGE);
     ASSERT(unknownArgumentMixedTestParser.getUnpositionalArgument(std::string("four")).value == "d");
+    ASSERT(unknownArgumentMixedTestParser.wrongUsageMessages.size() == 1);
+    ASSERT(unknownArgumentMixedTestParser.wrongUsageMessages.at(0) == "Unknown argument or flag(s): a123");
 
     delete[] unknownArgumentTestParameterList;
 
@@ -343,6 +359,8 @@ int main(int argc, char* argv[]) {
     ASSERT(unknownLongArgumentStandaloneTestParser.getUnpositionalArgument(std::string("four")).isError);
     ASSERT(unknownLongArgumentStandaloneTestParser.getUnpositionalArgument(std::string("four")).errorCode == ErrorCodes::NOT_PRESENT);
     ASSERT(unknownLongArgumentStandaloneTestParser.getUnpositionalArgument(std::string("four")).value == "");
+    ASSERT(unknownLongArgumentStandaloneTestParser.wrongUsageMessages.size() == 1);
+    ASSERT(unknownLongArgumentStandaloneTestParser.wrongUsageMessages.at(0) == "Unknown argument (or it's a flag that doesn't take a value): --a=123");
 
     int unknownLongArgumentMixedTestParameterCount = 7;
 
@@ -353,6 +371,8 @@ int main(int argc, char* argv[]) {
     ASSERT(unknownLongArgumentMixedTestParser.getUnpositionalArgument(std::string("four")).isError);
     ASSERT(unknownLongArgumentMixedTestParser.getUnpositionalArgument(std::string("four")).errorCode == ErrorCodes::WRONG_USAGE);
     ASSERT(unknownLongArgumentMixedTestParser.getUnpositionalArgument(std::string("four")).value == "d");
+    ASSERT(unknownLongArgumentMixedTestParser.wrongUsageMessages.size() == 1);
+    ASSERT(unknownLongArgumentMixedTestParser.wrongUsageMessages.at(0) == "Unknown argument (or it's a flag that doesn't take a value): --a=123");
 
     delete[] unknownLongArgumentTestParameterList;
     std::cout << "Passed unknown unpositional argument test." << std::endl;
@@ -374,7 +394,7 @@ int main(int argc, char* argv[]) {
     const char** incompleteArgumentTestParameterList = new const char*[6];
     incompleteArgumentTestParameterList[0] = "test";
     incompleteArgumentTestParameterList[1] = "-1";
-    incompleteArgumentTestParameterList[2] = "-2b";
+    incompleteArgumentTestParameterList[2] = "--two="; // value ""
     incompleteArgumentTestParameterList[3] = "-3c";
     incompleteArgumentTestParameterList[4] = "-4";
     incompleteArgumentTestParameterList[5] = "-5e";
@@ -387,6 +407,8 @@ int main(int argc, char* argv[]) {
     ASSERT(incompleteArgumentStandaloneTestParser.getUnpositionalArgument(std::string("four")).isError);
     ASSERT(incompleteArgumentStandaloneTestParser.getUnpositionalArgument(std::string("four")).errorCode == ErrorCodes::NOT_PRESENT);
     ASSERT(incompleteArgumentStandaloneTestParser.getUnpositionalArgument(std::string("four")).value == "");
+    ASSERT(incompleteArgumentStandaloneTestParser.wrongUsageMessages.size() == 1);
+    ASSERT(incompleteArgumentStandaloneTestParser.wrongUsageMessages.at(0) == "Argument expects value but has none: one");
 
     int incompleteArgumentMixedTestParameterCount = 6;
 
@@ -400,6 +422,9 @@ int main(int argc, char* argv[]) {
     ASSERT(incompleteArgumentMixedTestParser.getUnpositionalArgument('5').isError);
     ASSERT(incompleteArgumentMixedTestParser.getUnpositionalArgument('5').errorCode == ErrorCodes::WRONG_USAGE);
     ASSERT(incompleteArgumentMixedTestParser.getUnpositionalArgument('5').value == "e");
+    ASSERT(incompleteArgumentMixedTestParser.wrongUsageMessages.size() == 2);
+    ASSERT(incompleteArgumentMixedTestParser.wrongUsageMessages.at(0) == "Argument expects value but has none: one");
+    ASSERT(incompleteArgumentMixedTestParser.wrongUsageMessages.at(1) == "Argument expects value but has none: four");
 
     delete[] incompleteArgumentTestParameterList;
 
@@ -433,8 +458,11 @@ int main(int argc, char* argv[]) {
     ASSERT(incompleteLongArgumentStandaloneTestParser.getUnpositionalArgument(std::string("four")).isError);
     ASSERT(incompleteLongArgumentStandaloneTestParser.getUnpositionalArgument(std::string("four")).errorCode == ErrorCodes::NOT_PRESENT);
     ASSERT(incompleteLongArgumentStandaloneTestParser.getUnpositionalArgument(std::string("four")).value == "");
+    ASSERT(incompleteLongArgumentStandaloneTestParser.wrongUsageMessages.size() == 1);
+    ASSERT(incompleteLongArgumentStandaloneTestParser.wrongUsageMessages.at(0) == "Argument expects value but has none: one");
 
     int incompleteLongArgumentMixedTestParameterCount = 8;
+    incompleteLongArgumentTestPositionalArguments.push_back(CLI::PositionalArgument("arg", "argument"));
 
     CLI::ArgumentsParser incompleteLongArgumentMixedTestParser = CLI::ArgumentsParser(incompleteLongArgumentMixedTestParameterCount, incompleteLongArgumentTestParameterList, incompleteLongArgumentTestFlags, incompleteLongArgumentTestUnpositionalArguments, incompleteLongArgumentTestPositionalArguments);
     ASSERT(incompleteLongArgumentMixedTestParser.getUnpositionalArgument('1').isError);
@@ -449,6 +477,9 @@ int main(int argc, char* argv[]) {
     ASSERT(incompleteLongArgumentMixedTestParser.getUnpositionalArgument('5').isError);
     ASSERT(incompleteLongArgumentMixedTestParser.getUnpositionalArgument('5').errorCode == ErrorCodes::WRONG_USAGE);
     ASSERT(incompleteLongArgumentMixedTestParser.getUnpositionalArgument('5').value == "e");
+    ASSERT(incompleteLongArgumentMixedTestParser.wrongUsageMessages.size() == 2);
+    ASSERT(incompleteLongArgumentMixedTestParser.wrongUsageMessages.at(0) == "Argument expects value but has none: one");
+    ASSERT(incompleteLongArgumentMixedTestParser.wrongUsageMessages.at(1) == "Argument expects value but has none: four");
 
     delete[] incompleteLongArgumentTestParameterList;
     std::cout << "Passed incomplete unpositional argument test." << std::endl;
@@ -468,6 +499,7 @@ int main(int argc, char* argv[]) {
     tooFewArgumentsTestPositionalArguments.push_back(CLI::PositionalArgument("argument1", "test argument"));
     tooFewArgumentsTestPositionalArguments.push_back(CLI::PositionalArgument("argument2", "test argument"));
     tooFewArgumentsTestPositionalArguments.push_back(CLI::PositionalArgument("argument3", "test argument"));
+    tooFewArgumentsTestPositionalArguments.push_back(CLI::PositionalArgument("argument4", "test argument"));
 
     const char** tooFewArgumentsTestParameterList = new const char*[10];
     tooFewArgumentsTestParameterList[0] = "test";
@@ -499,6 +531,11 @@ int main(int argc, char* argv[]) {
     ASSERT(tooFewArgumentsStandaloneTestParser.getUnpositionalArgument('d').isError);
     ASSERT(tooFewArgumentsStandaloneTestParser.getUnpositionalArgument('d').errorCode == ErrorCodes::NOT_PRESENT);
     ASSERT(tooFewArgumentsStandaloneTestParser.getUnpositionalArgument('d').value == "");
+    ASSERT(tooFewArgumentsStandaloneTestParser.wrongUsageMessages.size() == 4);
+    ASSERT(tooFewArgumentsStandaloneTestParser.wrongUsageMessages.at(0) == "Too few positional arguments! Missing: argument1");
+    ASSERT(tooFewArgumentsStandaloneTestParser.wrongUsageMessages.at(1) == "Too few positional arguments! Missing: argument2");
+    ASSERT(tooFewArgumentsStandaloneTestParser.wrongUsageMessages.at(2) == "Too few positional arguments! Missing: argument3");
+    ASSERT(tooFewArgumentsStandaloneTestParser.wrongUsageMessages.at(3) == "Too few positional arguments! Missing: argument4");
 
     int tooFewArgumentsMixedTestParameterCount = 10;
     CLI::ArgumentsParser tooFewArgumentsMixedTestParser = CLI::ArgumentsParser(tooFewArgumentsMixedTestParameterCount, tooFewArgumentsTestParameterList, tooFewArgumentsTestFlags, tooFewArgumentsTestUnpositionalArguments, tooFewArgumentsTestPositionalArguments);
@@ -515,6 +552,9 @@ int main(int argc, char* argv[]) {
     ASSERT(tooFewArgumentsMixedTestParser.getPositionalArgument(3).isError);
     ASSERT(tooFewArgumentsMixedTestParser.getPositionalArgument(3).errorCode == ErrorCodes::NOT_PRESENT);
     ASSERT(tooFewArgumentsMixedTestParser.getPositionalArgument(3).value == "");
+    ASSERT(tooFewArgumentsMixedTestParser.getPositionalArgument(4).isError);
+    ASSERT(tooFewArgumentsMixedTestParser.getPositionalArgument(4).errorCode == ErrorCodes::NOT_PRESENT);
+    ASSERT(tooFewArgumentsMixedTestParser.getPositionalArgument(4).value == "");
     ASSERT(tooFewArgumentsMixedTestParser.getUnpositionalArgument('b').isError);
     ASSERT(tooFewArgumentsMixedTestParser.getUnpositionalArgument('b').errorCode == ErrorCodes::WRONG_USAGE);
     ASSERT(tooFewArgumentsMixedTestParser.getUnpositionalArgument('b').value == "1");
@@ -524,6 +564,9 @@ int main(int argc, char* argv[]) {
     ASSERT(tooFewArgumentsMixedTestParser.getUnpositionalArgument('d').isError);
     ASSERT(tooFewArgumentsMixedTestParser.getUnpositionalArgument('d').errorCode == ErrorCodes::WRONG_USAGE);
     ASSERT(tooFewArgumentsMixedTestParser.getUnpositionalArgument('d').value == "ddd");
+    ASSERT(tooFewArgumentsMixedTestParser.wrongUsageMessages.size() == 2);
+    ASSERT(tooFewArgumentsMixedTestParser.wrongUsageMessages.at(0) == "Too few positional arguments! Missing: argument3");
+    ASSERT(tooFewArgumentsMixedTestParser.wrongUsageMessages.at(1) == "Too few positional arguments! Missing: argument4");
 
     delete[] tooFewArgumentsTestParameterList;
     std::cout << "Passed too few positional arguments test." << std::endl;
@@ -568,6 +611,8 @@ int main(int argc, char* argv[]) {
     ASSERT(tooManyArgumentsStandaloneTestParser.getUnpositionalArgument('d').isError);
     ASSERT(tooManyArgumentsStandaloneTestParser.getUnpositionalArgument('d').errorCode == ErrorCodes::NOT_PRESENT);
     ASSERT(tooManyArgumentsStandaloneTestParser.getUnpositionalArgument('d').value == "");
+    ASSERT(tooManyArgumentsStandaloneTestParser.wrongUsageMessages.size() == 1);
+    ASSERT(tooManyArgumentsStandaloneTestParser.wrongUsageMessages.at(0) == "Too many positional arguments! Unexpected encounter of: positional_arg_1");
 
     int tooManyArgumentsMixedTestParameterCount = 10;
     CLI::ArgumentsParser tooManyArgumentsMixedTestParser = CLI::ArgumentsParser(tooManyArgumentsMixedTestParameterCount, tooManyArgumentsTestParameterList, tooManyArgumentsTestFlags, tooManyArgumentsTestUnpositionalArguments, tooManyArgumentsTestPositionalArguments);
@@ -584,6 +629,9 @@ int main(int argc, char* argv[]) {
     ASSERT(tooManyArgumentsMixedTestParser.getUnpositionalArgument('d').isError);
     ASSERT(tooManyArgumentsMixedTestParser.getUnpositionalArgument('d').errorCode == ErrorCodes::WRONG_USAGE);
     ASSERT(tooManyArgumentsMixedTestParser.getUnpositionalArgument('d').value == "ddd");
+    ASSERT(tooManyArgumentsMixedTestParser.wrongUsageMessages.size() == 2);
+    ASSERT(tooManyArgumentsMixedTestParser.wrongUsageMessages.at(0) == "Too many positional arguments! Unexpected encounter of: positional_arg_1");
+    ASSERT(tooManyArgumentsMixedTestParser.wrongUsageMessages.at(1) == "Too many positional arguments! Unexpected encounter of: positional_arg_2");
 
     delete[] tooManyArgumentsTestParameterList;
     std::cout << "Passed too many positional arguments test." << std::endl;