diff --git a/unittests/test__schema.py b/unittests/test__schema.py
new file mode 100644
index 0000000..567e69c
--- /dev/null
+++ b/unittests/test__schema.py
@@ -0,0 +1,8 @@
+from bo4e_generator.schema import camel_to_snake
+
+
+class TestSchema:
+    def test_camel_to_snake(self) -> None:
+        camelcasestring = "LastgangKompakt"
+        snakecasestring = "lastgang_kompakt"
+        assert snakecasestring == camel_to_snake(camelcasestring)
diff --git a/unittests/test_main.py b/unittests/test_main.py
index f49ec68..3d507c7 100644
--- a/unittests/test_main.py
+++ b/unittests/test_main.py
@@ -41,8 +41,9 @@ def test_main(self):
         assert __version__ == "0.6.1rc13"
 
     def test_resolve_paths(self) -> None:
-        relative_path_input = Path(INPUT_DIR)
+        relative_path_input = INPUT_DIR
         absolute_path_input = relative_path_input.resolve()
-        relative_path_output = Path(OUTPUT_DIR)
+        relative_path_output = OUTPUT_DIR
         absolute_path_output = relative_path_output.resolve()
         assert (absolute_path_input, absolute_path_output) == resolve_paths(INPUT_DIR, OUTPUT_DIR)
+        assert (absolute_path_input, absolute_path_output) == resolve_paths(absolute_path_input, absolute_path_output)
diff --git a/unittests/test_parser.py b/unittests/test_parser.py
new file mode 100644
index 0000000..0db90c3
--- /dev/null
+++ b/unittests/test_parser.py
@@ -0,0 +1,29 @@
+from pathlib import Path
+
+from datamodel_code_generator import DataModelType, PythonVersion
+from datamodel_code_generator.model import get_data_model_types
+
+from bo4e_generator.parser import OutputType, get_bo4e_data_model_types, remove_future_import
+from bo4e_generator.schema import get_namespace
+
+INPUT_DIR = Path("unittests/test_data/bo4e_schemas")
+
+
+class TestParser:
+    def test_get_bo4e_data_model_types(self) -> None:
+        namespace = get_namespace(INPUT_DIR)
+        data_model_types = get_bo4e_data_model_types(
+            DataModelType.PydanticV2BaseModel, target_python_version=PythonVersion.PY_311, namespace=namespace
+        )
+        data_model_types_compare = get_data_model_types(
+            DataModelType.PydanticV2BaseModel, target_python_version=PythonVersion.PY_311
+        )
+        assert (data_model_types.root_model) == data_model_types_compare.root_model
+        assert (data_model_types.field_model) == data_model_types_compare.field_model
+        assert (
+            data_model_types.dump_resolve_reference_action
+        ) == data_model_types_compare.dump_resolve_reference_action
+        assert (data_model_types.known_third_party) == data_model_types_compare.known_third_party
+
+    def test_remove_future_import(self) -> None:
+        assert ("") == remove_future_import("from __future__ import annotations\n\n", OutputType.PYDANTIC_V2)
diff --git a/unittests/test_sqlparser.py b/unittests/test_sqlparser.py
new file mode 100644
index 0000000..d2d7ef9
--- /dev/null
+++ b/unittests/test_sqlparser.py
@@ -0,0 +1,45 @@
+from collections import defaultdict
+from pathlib import Path
+from typing import Any, DefaultDict
+
+from bo4e_generator.schema import get_namespace
+from bo4e_generator.sqlparser import create_sql_field, return_ref, write_many_many_links
+
+INPUT_DIR = Path("unittests/test_data/bo4e_schemas")
+CLASSNAME = "Angebot"
+FIELDNAME = "_typ"
+
+
+class TestSQLParser:
+    def test_return_ref(self):
+        namespace = get_namespace(INPUT_DIR)
+        field_from_json = namespace[CLASSNAME].schema_parsed["properties"][FIELDNAME]
+        reference_name = return_ref(field_from_json, "$ref")
+        assert reference_name == "Typ"
+
+    def test_create_sql_field(self):
+        namespace = get_namespace(INPUT_DIR)
+        add_relation: DefaultDict[str, dict[str, Any]] = defaultdict(dict)
+        relation_imports: DefaultDict[str, dict[str, str]] = defaultdict(dict)
+        add_relation_comp: DefaultDict[str, dict[str, Any]] = defaultdict(dict)
+        relation_imports_comp: DefaultDict[str, dict[str, Any]] = defaultdict(dict)
+        add_relation, relation_imports = create_sql_field(
+            FIELDNAME, CLASSNAME, namespace, add_relation, relation_imports
+        )
+        add_relation_comp.update({"Angebot": {"typ": "Typ| None= Field(Typ.ANGEBOT)"}})
+        relation_imports_comp.update({"AngebotADD": {"Typ": "enum.typ"}})
+        assert add_relation == add_relation_comp
+        assert relation_imports == relation_imports_comp
+
+    def test_write_many_many_links(self):
+        links: dict[str, str] = {}
+        namespace = get_namespace(INPUT_DIR)
+        add_relation: DefaultDict[str, dict[str, Any]] = defaultdict(dict)
+        relation_imports: DefaultDict[str, dict[str, str]] = defaultdict(dict)
+        add_relation, relation_imports = create_sql_field(
+            "externeReferenzen", CLASSNAME, namespace, add_relation, relation_imports
+        )
+        links = add_relation["MANY"]
+        file_contents = write_many_many_links(links)
+        keywords = ["AngebotExterneReferenzLink", "angebot_id", "externereferenz_id"]
+        assert all(substring in file_contents for substring in keywords)