diff --git a/Start_Windows/bintree.c b/Start_Windows/bintree.c
index 5cf82a9..c2493c9 100644
--- a/Start_Windows/bintree.c
+++ b/Start_Windows/bintree.c
@@ -12,7 +12,45 @@
 // if isDuplicate is NULL, otherwise ignores duplicates and sets isDuplicate to 1 (or to 0 if a new entry is added).
 TreeNode *addToTree(TreeNode *root, const void *data, size_t dataSize, CompareFctType compareFct, int *isDuplicate)
 {
+    if (!data){
+        return NULL;
+    }
 
+    if (!root){
+        TreeNode *new = malloc(sizeof(TreeNode));
+        if (!new){
+            return NULL;
+        }
+        new->data = malloc(dataSize);
+        if (!new->data){
+            free(new);
+            return NULL;
+        }
+
+        memcpy(new->data, data, dataSize);
+        new->left = new->right = NULL;
+
+        if (isDuplicate){
+            *isDuplicate = 0;
+        }
+        return new;
+    }
+
+    int cmp = compareFct(data, root->data);
+
+    if (cmp < 0) {
+        root->left = addToTree(root->left, data, dataSize, compareFct, isDuplicate);
+    } else if (cmp > 0) {
+        root->right = addToTree(root->right, data, dataSize, compareFct, isDuplicate);
+    } else {
+        if (isDuplicate == NULL) {
+            root->left = addToTree(root->left, data, dataSize, compareFct, NULL);
+        } else {
+            *isDuplicate = 1;
+        }
+    }
+
+    return root;
 }
 
 // Iterates over the tree given by root. Follows the usage of strtok. If tree is NULL, the next entry of the last tree given is returned in ordering direction.
@@ -20,7 +58,7 @@ TreeNode *addToTree(TreeNode *root, const void *data, size_t dataSize, CompareFc
 // push the top node and push all its left nodes.
 void *nextTreeData(TreeNode *root)
 {
-
+    
 }
 
 // Releases all memory resources (including data copies).
diff --git a/Start_Windows/bintree.o b/Start_Windows/bintree.o
new file mode 100644
index 0000000..4a63186
Binary files /dev/null and b/Start_Windows/bintree.o differ
diff --git a/Start_Windows/bintreeTests.c b/Start_Windows/bintreeTests.c
new file mode 100644
index 0000000..f637281
--- /dev/null
+++ b/Start_Windows/bintreeTests.c
@@ -0,0 +1,72 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <math.h>
+#include "unity.h"
+#include "bintree.h"
+
+int compareInt(const void *arg1, const void *arg2) {
+    int a = *(const int *)arg1;
+    int b = *(const int *)arg2;
+    return a - b;
+}
+int compareString(const void *arg1, const void *arg2) {
+    const char *str1 = (const char *)arg1;
+    const char *str2 = (const char *)arg2;
+    return strcmp(str1, str2);
+}
+
+
+
+
+static void testAddToTreeNewRoot(){
+    TreeNode *root=NULL;
+    int a = 1;
+    root = addToTree(root,&a, sizeof(int),compareInt,0);
+
+    TEST_ASSERT_EQUAL_INT(a,*(int*)(root->data));
+}
+
+static void testAddToTreeToExistingRoot(){
+    TreeNode *root=NULL;
+    int a = 1;
+    int b = 3;
+    int c = 4;
+    int d = 2;
+    root = addToTree(root,&a, sizeof(int),compareInt,0);
+    root = addToTree(root,&b, sizeof(int),compareInt,0);
+    root = addToTree(root,&c, sizeof(int),compareInt,0);
+    root = addToTree(root,&d, sizeof(int),compareInt,0);
+
+    TEST_ASSERT_EQUAL_INT(a,*(int*)(root->data));
+    TEST_ASSERT_EQUAL_INT(b,*(int*)(root->right->data));
+    TEST_ASSERT_EQUAL_INT(c,*(int*)(root->right->right->data));
+    TEST_ASSERT_EQUAL_INT(d,*(int*)(root->right->left->data));
+}
+static void testAddToTreeNoData(){
+    TreeNode *root=NULL;
+    root = addToTree(root,NULL, sizeof(int),compareInt,0);
+
+    TEST_ASSERT_NULL(root);
+}
+
+
+void setUp(void){
+    
+}
+void tearDown(void){
+
+}
+
+
+
+int main(){
+    UNITY_BEGIN();
+    printf("\n============================\nBintree tests\n============================\n");
+    
+    RUN_TEST(testAddToTreeNewRoot);
+    RUN_TEST(testAddToTreeToExistingRoot);
+    RUN_TEST(testAddToTreeNoData);
+
+    return UNITY_END();
+}
\ No newline at end of file
diff --git a/Start_Windows/makefile b/Start_Windows/makefile
index b3d0844..0965468 100644
--- a/Start_Windows/makefile
+++ b/Start_Windows/makefile
@@ -29,6 +29,10 @@ unitTests:
 stackTests: stack.o stackTests.c $(unityfolder)/unity.c
 	$(CC) $(CFLAGS) -I$(unityfolder) -o runStackTests stackTests.c stack.o $(unityfolder)/unity.c
 
+bintreeTests: stack.o bintree.o bintreeTests.c $(unityfolder)/unity.c
+	$(CC) $(CFLAGS) -I$(unityfolder) -o runBintreeTests bintreeTests.c stack.o bintree.o $(unityfolder)/unity.c
+
+
 # --------------------------
 # Clean
 # --------------------------
diff --git a/Start_Windows/runBintreeTests.exe b/Start_Windows/runBintreeTests.exe
new file mode 100644
index 0000000..bda5ff1
Binary files /dev/null and b/Start_Windows/runBintreeTests.exe differ