Add a test for the creating source feature.

features/creating_source.feature

@@ -0,0 +1,8 @@
+Feature: Creating the source
+
+  Scenario: Adding an new unique source
+    Given the label "db"
+    And the path "/db"
+    When I add the source
+    Then the source should be added successfully
+

features/steps/creating_source_steps.py

@@ -0,0 +1,35 @@
+from behave import given, when, then
+from peewee import IntegrityError
+from tui_rsync.models.models import create_tables
+from tui_rsync.models.models import Source
+
+@given('the label "{label}"')
+def given_source_label(context, label):
+    create_tables()
+    context.label = label
+
+@given('the path "{source_path}"')
+def given_source_path(context, source_path):
+    context.source_path = source_path
+
+@when('I add the source')
+def add_source(context):
+    try:
+        context.source = Source.create_save(
+            context.label,
+            context.source_path,
+            [],
+            "",
+        )
+    except IntegrityError:
+        context.exception_raised = True
+    else:
+        context.exception_raised = False
+
+@then('the source should be added successfully')
+def path_has_added(context):
+    assert context.exception_raised == False
+
+    assert context.source.label  == context.label
+    assert context.source.source.path == context.source_path
+