diff --git a/README.md b/README.md
index 643c17a..b761d21 100644
--- a/README.md
+++ b/README.md
@@ -1,2 +1,5 @@
-# dart_mock
+# Beispiel Programmieren gegen Interfaces
+
+* `dart run` - Startet Programm mit Sqlite-Backend
+* `dart test` - Testet mit Map-Backend
 
diff --git a/analysis_options.yaml b/analysis_options.yaml
new file mode 100644
index 0000000..61b6c4d
--- /dev/null
+++ b/analysis_options.yaml
@@ -0,0 +1,29 @@
+# This file configures the analyzer, which statically analyzes Dart code to
+# check for errors, warnings, and lints.
+#
+# The issues identified by the analyzer are surfaced in the UI of Dart-enabled
+# IDEs (https://dart.dev/tools#ides-and-editors). The analyzer can also be
+# invoked from the command line by running `flutter analyze`.
+
+# The following line activates a set of recommended lints for Flutter apps,
+# packages, and plugins designed to encourage good coding practices.
+include: package:flutter_lints/flutter.yaml
+
+linter:
+  # The lint rules applied to this project can be customized in the
+  # section below to disable rules from the `package:flutter_lints/flutter.yaml`
+  # included above or to enable additional rules. A list of all available lints
+  # and their documentation is published at
+  # https://dart-lang.github.io/linter/lints/index.html.
+  #
+  # Instead of disabling a lint rule for the entire project in the
+  # section below, it can also be suppressed for a single line of code
+  # or a specific dart file by using the `// ignore: name_of_lint` and
+  # `// ignore_for_file: name_of_lint` syntax on the line or in the file
+  # producing the lint.
+  rules:
+    # avoid_print: false  # Uncomment to disable the `avoid_print` rule
+    # prefer_single_quotes: true  # Uncomment to enable the `prefer_single_quotes` rule
+
+# Additional information about this file can be found at
+# https://dart.dev/guides/language/analysis-options
diff --git a/bin/mock.dart b/bin/mock.dart
new file mode 100644
index 0000000..e745955
--- /dev/null
+++ b/bin/mock.dart
@@ -0,0 +1,43 @@
+import 'package:mock/person.dart';
+import 'package:mock/business.dart';
+import 'package:mock/person_data_access_map.dart';
+import 'package:mock/person_data_access_sqlite.dart';
+
+/*
+ @startuml
+class Business {
+- PersonDataAccessMap backend
+}
+PersonDataAccessMap <-left- Business : uses
+
+class PersonDataAccessMap {
+- Map<int, Person> map
+ + store(Person p): void
+ + retrieve(int id): Person
+ + retrieveAll(): List<Person>
+}
+
+class PersonDataAccessSqlite implements PersonDataAccessMap {
+- Sqlite db
+ + store(Person p): void
+ + retrieve(int id): Person
+ + retrieveAll(): List<Person>
+}
+@enduml
+ */
+void main() {
+  PersonDataAccessMap backend = PersonDataAccessSqlite("sqlite3.db");
+  Business b = Business(backend);
+
+  List<Person> persons = b.getAllPersons();
+  int personCount = persons.length;
+
+  print("We know $personCount persons");
+
+  int nextPersonId = ++personCount;
+  b.addPerson(Person(nextPersonId, "A New Person"));
+
+  print("Now we know ${b.getAllPersons().length} persons");
+
+  backend.close();
+}
diff --git a/lib/business.dart b/lib/business.dart
new file mode 100644
index 0000000..a24db4e
--- /dev/null
+++ b/lib/business.dart
@@ -0,0 +1,14 @@
+import 'person.dart';
+import 'person_data_access_map.dart';
+
+class Business {
+  final PersonDataAccessMap _backend;
+
+  Business(this._backend);
+
+  void addPerson(Person p) => _backend.store(p);
+
+  bool existsPersonId(int id) => _backend.retrieve(id) != null;
+
+  List<Person> getAllPersons() => _backend.retrieveAll();
+}
diff --git a/lib/person.dart b/lib/person.dart
new file mode 100644
index 0000000..929abbe
--- /dev/null
+++ b/lib/person.dart
@@ -0,0 +1,9 @@
+class Person {
+  final int id;
+  final String name;
+
+  const Person(this.id, this.name);
+
+  @override
+  String toString() => "Person: $name ($id)";
+}
diff --git a/lib/person_data_access_map.dart b/lib/person_data_access_map.dart
new file mode 100644
index 0000000..7ec863b
--- /dev/null
+++ b/lib/person_data_access_map.dart
@@ -0,0 +1,13 @@
+import 'person.dart';
+
+class PersonDataAccessMap {
+  final Map<int, Person> _persons = {};
+
+  void store(Person p) => _persons[p.id] = p;
+
+  Person? retrieve(int personId) => _persons[personId];
+
+  List<Person> retrieveAll() => _persons.values.toList();
+
+  void close() {}
+}
diff --git a/lib/person_data_access_sqlite.dart b/lib/person_data_access_sqlite.dart
new file mode 100644
index 0000000..8f287bc
--- /dev/null
+++ b/lib/person_data_access_sqlite.dart
@@ -0,0 +1,48 @@
+import 'person.dart';
+import 'package:sqlite3/sqlite3.dart';
+
+import 'person_data_access_map.dart';
+
+class PersonDataAccessSqlite implements PersonDataAccessMap {
+  final String fileName;
+  final Database db;
+
+  PersonDataAccessSqlite(this.fileName) : db = sqlite3.open(fileName) {
+    try {
+      // when select fails due to missing table ...
+      db.execute('SELECT count(*) from persons');
+    } catch (e) {
+      // ... create it
+      db.execute('''CREATE TABLE persons (
+        id INTEGER NOT NULL PRIMARY KEY,
+        name TEXT NOT NULL);''');
+    }
+  }
+
+  @override
+  void store(Person p) {
+    final stmt = db.prepare('INSERT INTO persons (id, name) VALUES (?, ?)');
+    stmt.execute([p.id, p.name]);
+    stmt.dispose();
+  }
+
+  @override
+  Person? retrieve(int id) {
+    final ResultSet resultSet =
+        db.select('SELECT * FROM persons WHERE id = ?', [id]);
+    return resultSet.isEmpty
+        ? null
+        : Person(resultSet.first['id'], resultSet.first['name']);
+  }
+
+  @override
+  List<Person> retrieveAll() {
+    final ResultSet resultSet = db.select('SELECT * FROM persons');
+    return resultSet.map((row) => Person(row['id'], row['name'])).toList();
+  }
+
+  @override
+  void close() {
+    db.dispose();
+  }
+}
diff --git a/mock.iml b/mock.iml
new file mode 100644
index 0000000..899e825
--- /dev/null
+++ b/mock.iml
@@ -0,0 +1,14 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<module type="WEB_MODULE" version="4">
+  <component name="NewModuleRootManager" inherit-compiler-output="true">
+    <exclude-output />
+    <content url="file://$MODULE_DIR$">
+      <excludeFolder url="file://$MODULE_DIR$/.pub" />
+      <excludeFolder url="file://$MODULE_DIR$/.dart_tool" />
+      <excludeFolder url="file://$MODULE_DIR$/build" />
+    </content>
+    <orderEntry type="sourceFolder" forTests="false" />
+    <orderEntry type="library" name="Dart SDK" level="project" />
+    <orderEntry type="library" name="Dart Packages" level="project" />
+  </component>
+</module>
\ No newline at end of file
diff --git a/mock.puml b/mock.puml
new file mode 100644
index 0000000..1ea36be
--- /dev/null
+++ b/mock.puml
@@ -0,0 +1,21 @@
+@startuml
+class Business {
+- PersonDataAccess backend
+}
+PersonDataAccess <-left- Business : uses
+
+interface PersonDataAccess {
+ + store(Person p): void
+ + retrieve(int id): Person
+ + retrieveAll(): List<Person>
+}
+
+class PersonDataAccessMap implements PersonDataAccess {
+- Map<int, Person> map
+}
+
+class PersonDataAccessSqlite implements PersonDataAccess {
+- Sqlite db
+}
+
+@enduml
\ No newline at end of file
diff --git a/pubspec.yaml b/pubspec.yaml
new file mode 100644
index 0000000..c9670e5
--- /dev/null
+++ b/pubspec.yaml
@@ -0,0 +1,13 @@
+name: mock
+description: A simple Mock example
+version: 1.0.0
+
+environment:
+  sdk: '>=2.18.0 <3.0.0'
+
+dev_dependencies:
+  lints: ^2.0.0
+  test:
+
+dependencies: 
+  sqlite3: ^1.2.0
diff --git a/test/business_test.dart b/test/business_test.dart
new file mode 100644
index 0000000..fb76d3e
--- /dev/null
+++ b/test/business_test.dart
@@ -0,0 +1,39 @@
+import 'package:mock/person_data_access_map.dart';
+import 'package:test/test.dart';
+import 'package:mock/person.dart';
+import 'package:mock/business.dart';
+
+class TestPersonBackend extends PersonDataAccessMap {
+  TestPersonBackend() {
+    store(Person(1, "Mr. X"));
+    store(Person(2, "Ms. Y"));
+  }
+}
+
+void main() {
+  group('Backend', () {
+    PersonDataAccessMap? backend;
+
+    tearDownAll(() {
+      backend?.close();
+    });
+
+    group('Empty', () {
+      final PersonDataAccessMap backend = PersonDataAccessMap();
+      final Business business = Business(backend);
+
+      test('Initial size', () {
+        expect(business.getAllPersons().length, 0);
+      });
+    });
+
+    group('Filled', () {
+      final PersonDataAccessMap backend = TestPersonBackend();
+      final Business business = Business(backend);
+
+      test('Initial size', () {
+        expect(business.getAllPersons().length, 2);
+      });
+    });
+  });
+}
diff --git a/test/person_test.dart b/test/person_test.dart
new file mode 100644
index 0000000..fd21777
--- /dev/null
+++ b/test/person_test.dart
@@ -0,0 +1,36 @@
+import 'package:test/test.dart';
+import 'package:mock/person.dart';
+
+void main() {
+  group('Person properties', () {
+    final Person p1 = Person(1, "Dummy User");
+
+    setUp(() {
+      // runs before each test;
+      print("Set up");
+    });
+
+    tearDown(() {
+      // runs after each test;
+      print("Tear down");
+    });
+    test('id', () {
+      expect(p1.id, 1);
+    });
+
+    test('name', () {
+      expect(p1.id, 1);
+    });
+  });
+
+  group('Comparing persons', () {
+    final Person p1 = Person(1, "One person");
+    final Person p2 = Person(2, "Another person");
+    test('Same object', () {
+      expect(p1 == p1, true);
+    });
+    test('Different objects', () {
+      expect(p1 != p2, true);
+    });
+  });
+}