diff --git a/README.md b/README.md
index f50f0f7..75cf8c0 100644
--- a/README.md
+++ b/README.md
@@ -208,7 +208,7 @@ fiable_db.find_one(id=1) # Default table
 Save the database to a file.
 
 ```python
-fiable_db.save(filename, data)
+fiable_db.save()
 ```
 
 ### Other help functions
@@ -229,6 +229,14 @@ Load a file into the database.
 fiable_db.load(filename)
 ```
 
+### Save file
+
+Save a file into the database.
+
+```python
+fiable_db.save(filename)
+```
+
 ## Implementations in other languages
 
 - [Clojure](https://github.com/Toni-zgz/db_inmutable).
diff --git a/fiable_db.py b/fiable_db.py
index a3ad9b8..6b09282 100644
--- a/fiable_db.py
+++ b/fiable_db.py
@@ -17,8 +17,7 @@ class TypeData(TypedDict):
 
 Type_Data_List = Tuple[TypeData]
 Type_Add_Data = Union[Dict, Sequence[Dict]]
-Type_Add_Return = Union[Tuple[int, int, Dict],
-                        Tuple[Tuple[int, int, Dict]], None]
+Type_Add_Return = Union[Tuple[int, int, Dict], Tuple[Tuple[int, int, Dict]], None]
 Type_Update_Return = Union[Tuple[Tuple[int, int, Dict]]]
 Type_Delete_Return = Union[Tuple[Tuple[int, int, Dict]]]
 Type_Find_One_Return = TypeData
@@ -26,6 +25,7 @@ Type_Find_All_Return = Tuple[Type_Find_One_Return]
 
 # Functions
 
+
 def get_next_id(table: str = "default") -> int:
     """Get the next id for a table"""
     global database
@@ -39,18 +39,20 @@ def start(file_name: str = "") -> str:
     Returns:
         str: The file used
     """
+    global FILE
     global database
-    my_file_name = file_name if file_name else FILE
+    my_file_name = file_name if file_name != "" else FILE
     if path.exists(my_file_name):
         # Load the database
         load(my_file_name)
     else:
         # Create the database
-        save(my_file_name, database)
+        database = []
+        save(my_file_name)
     return my_file_name
 
 
-def save(file_name: str = "", data: TypeData = {}) -> bool:
+def save(file_name: str = "") -> bool:
     """Save the database
     Args:
         file_name (str, optional): The file to save to. Defaults to "".
@@ -58,10 +60,11 @@ def save(file_name: str = "", data: TypeData = {}) -> bool:
     Returns:
         bool: True if the data was saved, False otherwise
     """
+    global FILE
     global database
-    my_file_name = file_name if file_name else FILE
+    my_file_name = file_name if file_name != "" else FILE
     with open(my_file_name, "w") as f:
-        database = json.dump({}, f)
+        json.dump(database, f)
     return True
 
 
diff --git a/test/test_add.py b/test/test_add.py
index 46c1117..c9acab3 100644
--- a/test/test_add.py
+++ b/test/test_add.py
@@ -11,7 +11,6 @@ def test_add_two():
     """Add two items to the database."""
     add({"name": "John", "age": 12})
     add({"name": "Jane", "age": 34})
-    print(get_database())
     assert get_database() == [
         {"id": 1, "rev": 1, "data": {"name": "John", "age": 42}},
         {"id": 2, "rev": 1, "data": {"name": "John", "age": 12}},
diff --git a/test/test_save.py b/test/test_save.py
new file mode 100644
index 0000000..44a4e1c
--- /dev/null
+++ b/test/test_save.py
@@ -0,0 +1,47 @@
+import os
+from fiable_db import start, add, save, get_database, load
+
+filename = "fiabledb.json"
+
+def delete_file():
+    """Delete the database file."""
+    if os.path.exists(filename):
+        os.remove(filename)
+    
+def test_save_empty():
+    """Test that save() works when the database is empty."""
+    delete_file()
+    start()
+    save()
+    global database
+    database = []
+    load()
+    assert get_database() == []
+
+
+def test_save_one():
+    """Test that save() works when the database has one entry."""
+    delete_file()
+    start()
+    add({"name": "John", "age": 30})
+    save()
+    global database
+    database = []
+    load()
+    assert get_database() == [{"id": 1, "rev": 1, "data": {"name": "John", "age": 30}}]
+
+
+def test_save_two():
+    """Test that save() works when the database has two entries."""
+    delete_file()
+    start()
+    add({"name": "John", "age": 30})
+    add({"name": "Jane", "age": 28})
+    save()
+    global database
+    database = []
+    load()
+    assert get_database() == [
+        {"id": 1, "rev": 1, "data": {"name": "John", "age": 30}},
+        {"id": 2, "rev": 1, "data": {"name": "Jane", "age": 28}},
+    ]