diff --git a/src/com/annimon/ownlang/Main.java b/src/com/annimon/ownlang/Main.java
index dbd6a8b..499de79 100644
--- a/src/com/annimon/ownlang/Main.java
+++ b/src/com/annimon/ownlang/Main.java
@@ -94,6 +94,7 @@ public final class Main {
         } finally {
             if (showMeasurements) {
                 measurement.stop("Execution time");
+                System.out.println("======================");
                 System.out.println(measurement.summary(TimeUnit.MILLISECONDS, true));
             }
         }
diff --git a/src/com/annimon/ownlang/lib/Functions.java b/src/com/annimon/ownlang/lib/Functions.java
index eda7d0c..211de95 100644
--- a/src/com/annimon/ownlang/lib/Functions.java
+++ b/src/com/annimon/ownlang/lib/Functions.java
@@ -11,11 +11,14 @@ import java.util.Map;
 public final class Functions {
 
     private static final Map<String, Function> functions;
-    
     static {
         functions = new HashMap<>();
     }
     
+    public static Map<String, Function> getFunctions() {
+        return functions;
+    }
+    
     public static boolean isExists(String key) {
         return functions.containsKey(key);
     }
diff --git a/src/com/annimon/ownlang/lib/modules/ounit.java b/src/com/annimon/ownlang/lib/modules/ounit.java
new file mode 100644
index 0000000..25c8f80
--- /dev/null
+++ b/src/com/annimon/ownlang/lib/modules/ounit.java
@@ -0,0 +1,142 @@
+package com.annimon.ownlang.lib.modules;
+
+import com.annimon.ownlang.lib.*;
+import java.text.DecimalFormat;
+import java.util.List;
+import java.util.stream.Collectors;
+
+/**
+ *
+ * @author aNNiMON
+ */
+public final class ounit implements Module {
+
+    @Override
+    public void init() {
+        Functions.set("assertEquals", new assertEquals());
+        Functions.set("assertNotEquals", new assertNotEquals());
+        Functions.set("assertSameType", new assertSameType());
+        Functions.set("assertTrue", new assertTrue());
+        Functions.set("assertFalse", new assertFalse());
+        Functions.set("runTests", new runTests());
+    }
+    
+    private static String microsToSeconds(long micros) {
+        return new DecimalFormat("#0.0000").format(micros / 1000d / 1000d) + " sec";
+    }
+    
+    private static class assertEquals implements Function {
+        @Override
+        public Value execute(Value... args) {
+            if (args[0].equals(args[1])) return NumberValue.ONE;
+            throw new OUnitAssertionException("Values are not equals: "
+                    + "1: " + args[0] + ", 2: " + args[1]);
+        }
+    }
+    
+    private static class assertNotEquals implements Function {
+        @Override
+        public Value execute(Value... args) {
+            if (!args[0].equals(args[1])) return NumberValue.ONE;
+            throw new OUnitAssertionException("Values are equals: " + args[0]);
+        }
+    }
+    
+    private static class assertSameType implements Function {
+        @Override
+        public Value execute(Value... args) {
+            if (args[0].type() == args[1].type()) return NumberValue.ONE;
+            throw new OUnitAssertionException("Types mismatch. "
+                    + "1: " + Types.typeToString(args[0].type())
+                    + ", 2: " + Types.typeToString(args[1].type()));
+        }
+    }
+    
+    private static class assertTrue implements Function {
+        @Override
+        public Value execute(Value... args) {
+            if (args[0].asInt() != 0) return NumberValue.ONE;
+            throw new OUnitAssertionException("Expected true, but found false.");
+        }
+    }
+    
+    private static class assertFalse implements Function {
+        @Override
+        public Value execute(Value... args) {
+            if (args[0].asInt() == 0) return NumberValue.ONE;
+            throw new OUnitAssertionException("Expected false, but found true.");
+        }
+    }
+    
+    private static class runTests implements Function {
+        
+        @Override
+        public Value execute(Value... args) {
+            List<TestInfo> tests = Functions.getFunctions().entrySet().stream()
+                    .filter(e -> e.getKey().toLowerCase().startsWith("test"))
+                    .map(e -> runTest(e.getKey(), e.getValue()))
+                    .collect(Collectors.toList());
+            
+            int failures = 0;
+            long summaryTime = 0;
+            final StringBuilder result = new StringBuilder();
+            for (TestInfo test : tests) {
+                if (!test.isPassed) failures++;
+                summaryTime += test.elapsedTimeInMicros;
+                result.append(System.lineSeparator());
+                result.append(test.info());
+            }
+            result.append(System.lineSeparator());
+            result.append(String.format("Tests run: %d, Failures: %d, Time elapsed: %s",
+                    tests.size(), failures,
+                    microsToSeconds(summaryTime)));
+            return new StringValue(result.toString());
+        }
+        
+        private TestInfo runTest(String name, Function f) {
+            final long startTime = System.nanoTime();
+            boolean isSuccessfull;
+            String failureDescription;
+            try {
+                f.execute();
+                isSuccessfull = true;
+                failureDescription = "";
+            } catch (OUnitAssertionException oae) {
+                isSuccessfull = false;
+                failureDescription = oae.getMessage();
+            }
+            final long elapsedTime = System.nanoTime() - startTime;
+            return new TestInfo(name, isSuccessfull, failureDescription, elapsedTime / 1000);
+        }
+    }
+    
+    private static class OUnitAssertionException extends RuntimeException {
+
+        public OUnitAssertionException(String message) {
+            super(message);
+        }
+    }
+    
+    private static class TestInfo {
+        String name;
+        boolean isPassed;
+        String failureDescription;
+        long elapsedTimeInMicros;
+
+        public TestInfo(String name, boolean isPassed, String failureDescription, long elapsedTimeInMicros) {
+            this.name = name;
+            this.isPassed = isPassed;
+            this.failureDescription = failureDescription;
+            this.elapsedTimeInMicros = elapsedTimeInMicros;
+        }
+        
+        public String info() {
+            return String.format("%s [%s]\n%sElapsed: %s\n",
+                    name,
+                    isPassed ? "passed" : "FAILED",
+                    isPassed ? "" : (failureDescription + "\n"),
+                    microsToSeconds(elapsedTimeInMicros)
+            );
+        }
+    }
+}
diff --git a/tests.own b/tests.own
new file mode 100644
index 0000000..c3ea230
--- /dev/null
+++ b/tests.own
@@ -0,0 +1,39 @@
+use "ounit"
+
+def testAdditionOnNumbers() {
+  assertEquals(6, 0 + 1 + 2 + 3)
+}
+
+def testSubtractionOnNumbers() {
+  assertEquals(-6, 0 - 1 - 2 - 3)
+}
+
+def testPrefixIncrement() {
+  a = 8
+  assertEquals(9, ++a)
+  assertEquals(9, a)
+}
+
+def testPostfixIncrement() {
+  a = 8
+  assertEquals(8, a++)
+  assertEquals(9, a)
+}
+
+def testStringReversing() {
+  assertEquals("tset", -"test")
+}
+
+def testStringMultiplication() {
+  assertEquals("******", "*" * 6)
+}
+
+def testTypes() {
+  assertSameType(0, 0.0)
+}
+
+def testFail() {
+  assertTrue(false)
+}
+
+println runTests()
\ No newline at end of file