diff --git a/include/Lexer.h b/include/Lexer.h
index 8e87d84..02223a9 100644
--- a/include/Lexer.h
+++ b/include/Lexer.h
@@ -16,9 +16,10 @@ class Lexer {
 		void addRegEx(std::string regExString);
 		void setInput(std::string inputString);
 		Symbol next();
+		static void test();
 	private:
 		std::vector<RegEx*> regExs;
 		std::string input;
 		int currentPosition;
 };
-#endif
\ No newline at end of file
+#endif
diff --git a/main.cpp b/main.cpp
index 1c1bf8e..fb254d1 100644
--- a/main.cpp
+++ b/main.cpp
@@ -19,6 +19,7 @@
 int main(int argc, char* argv[]) {
 	if (argc == 2 && std::string(argv[1]) == "--test") {
 		StringReader::test();
+		Lexer::test();
 		return 0;
 	}
 
diff --git a/src/Lexer.cpp b/src/Lexer.cpp
index 72055ea..1dcb4da 100644
--- a/src/Lexer.cpp
+++ b/src/Lexer.cpp
@@ -1,4 +1,5 @@
 #include "Lexer.h"
+#include <cassert>
 
 Lexer::Lexer() {
 	//Do nothing
@@ -25,7 +26,7 @@ void Lexer::addRegEx(std::string regExString) {
 Symbol Lexer::next() {
 	//std::cout << "Current at is \"" << input.substr(currentPosition,input.length()-1) << "\" currentPos is " << currentPosition  << " out of " << input.length() <<std::endl;
 	//If we're at the end, return an eof
-	if (currentPosition >= input.length()-1)
+	if (currentPosition >= input.length())
 		return Symbol("$EOF$", true);
 	int longestMatch = -1;
 	RegEx* longestRegEx = NULL;
@@ -48,4 +49,48 @@ Symbol Lexer::next() {
 		//std::cout << "Remaining is ||" << input.substr(currentPosition,input.length()-1) << "||" << std::endl;
 		return Symbol();
 	}
-}
\ No newline at end of file
+}
+
+void Lexer::test() {
+    Symbol s;
+    {
+        Lexer lex;
+        lex.addRegEx("b");
+        lex.setInput("bb");
+        s = lex.next();
+        assert(s.getName() == "b" && s.getValue() == "b");
+        s = lex.next();
+        assert(s.getName() == "b" && s.getValue() == "b");
+        assert(lex.next() == Symbol("$EOF$", true));
+    }
+
+    {
+        Lexer lex;
+        lex.addRegEx("a*");
+        lex.addRegEx("b");
+        lex.setInput("aaabaabb");
+        s = lex.next();
+        assert(s.getName() == "a*" && s.getValue() == "aaa");
+        s = lex.next();
+        assert(s.getName() == "b" && s.getValue() == "b");
+        s = lex.next();
+        assert(s.getName() == "a*" && s.getValue() == "aa");
+        s = lex.next();
+        assert(s.getName() == "b" && s.getValue() == "b");
+        s = lex.next();
+        assert(s.getName() == "b" && s.getValue() == "b");
+        assert(lex.next() == Symbol("$EOF$", true));
+    }
+
+    // Test a lexer error condition.
+    {
+        Lexer lex;
+        lex.addRegEx("a|b");
+        lex.setInput("blah");
+        s = lex.next();
+        assert(s.getName() == "a|b" && s.getValue() == "b");
+        assert(lex.next() == Symbol());
+    }
+
+    std::cout << "Lexer tests passed\n";
+}