diff --git a/virtual/cores/virtual/main.cpp b/virtual/cores/virtual/main.cpp
index 2c23272..c7c1fd1 100644
--- a/virtual/cores/virtual/main.cpp
+++ b/virtual/cores/virtual/main.cpp
@@ -29,6 +29,12 @@ void initVariant() { }
 void setupUSB() __attribute__((weak));
 void setupUSB() { }
 
+// This function can be overridden in other libraries
+// e.g. to run a testing framework.
+//
+__attribute__((weak))
+extern void executeTestFunction();
+
 void init(void) {
   // Arduino core does some device-related setup here.
   // We don't need to do anything.
@@ -36,6 +42,13 @@ void init(void) {
 
 int main(int argc, char* argv[]) {
   if (!initVirtualInput(argc, argv)) return 1;
+  
+  if(testFunctionExecutionRequested()) {
+     if(executeTestFunction) {
+        executeTestFunction();
+     }
+     return 0;
+  }
 
   init();
   initVariant();
@@ -51,4 +64,3 @@ int main(int argc, char* argv[]) {
 
   return 0;
 }
-
diff --git a/virtual/cores/virtual/virtual_io.cpp b/virtual/cores/virtual/virtual_io.cpp
index d40fd6f..9cd2f1d 100644
--- a/virtual/cores/virtual/virtual_io.cpp
+++ b/virtual/cores/virtual/virtual_io.cpp
@@ -8,7 +8,8 @@
 #include <sys/stat.h>  // mkdir()
 #include <errno.h>
 
-static bool interactive;
+static bool interactive = false;
+static bool test_function = false;
 static std::istream* input = NULL;
 static std::ostream* usbstream = NULL;
 static std::ostream* ledstream = NULL;
@@ -18,6 +19,10 @@ bool isInteractive(void) {
   return interactive;
 }
 
+bool testFunctionExecutionRequested() {
+  return test_function;
+}
+
 unsigned currentCycle(void) {
   return cycle;
 }
@@ -58,6 +63,8 @@ bool initVirtualInput(int argc, char* argv[]) {
   if (strcmp(argv[1], "-i") == 0) {
     interactive = true;
     input = &std::cin;
+  } else if(strcmp(argv[1], "-t") == 0) {
+    test_function = true;
   } else {
     interactive = false;
     input = new std::ifstream(argv[1]);
@@ -95,6 +102,7 @@ void printHelp(void) {
   std::cout << "This program expects a single argument, which is either:" << std::endl;
   std::cout << "  1. An input file/script, with format given below, or" << std::endl;
   std::cout << "  2. \"-i\", to run interactively, where you can interactively enter commands and see results." << std::endl;
+  std::cout << "  3. \"-t\", to run a test function that is specified in the sketch file." << std::endl;
   std::cout << "\nIn either case, for each scan cycle you will specify zero or more input 'commands', that is," << std::endl;
   std::cout << "  actions to take on the keys of the virtual keyboard.  Each line of the input file, or each" << std::endl;
   std::cout << "  prompt (in interactive mode), represents one scan cycle; a blank line or empty prompt means" << std::endl;
diff --git a/virtual/cores/virtual/virtual_io.h b/virtual/cores/virtual/virtual_io.h
index 848cbb1..605aa74 100644
--- a/virtual/cores/virtual/virtual_io.h
+++ b/virtual/cores/virtual/virtual_io.h
@@ -10,6 +10,7 @@ bool initVirtualInput(int argc, char* argv[]);
 
 std::string getLineOfInput(bool anythingHeld);
 bool isInteractive(void);
+bool testFunctionExecutionRequested();
 void printHelp(void);
 
 unsigned currentCycle(void);  // current cycle number, first cycle is 0