diff --git a/presentation/slides/03-integration-testing.md b/presentation/slides/03-integration-testing.md
index 200cfa4..5f51103 100644
--- a/presentation/slides/03-integration-testing.md
+++ b/presentation/slides/03-integration-testing.md
@@ -13,26 +13,18 @@
 
 ---
 
-```csharp
-// Arrange
-var mailer = Substitute.For<IMailer>();
-
-var validCustomer = new ValidCustomer();
-
-// We inject an interface to the system-under-test!
-// Mocking frameworks can control the behaviour of the injected object!
-var sut = new RegistrationService(mailer);
-
-// Act
-sut.Register(validCustomer);
+## Test matrix
 
-// Assert
-mailer.Received().Send();
-```
+![test-matrix](images/test-matrix.png)
 
 ---
 
-## What should we test?
+## Test matrix - Code smell
+
+- "overcomplicated code" quadrant
+  - wrong layer of abstraction 
+  - missing encapsulation
+- solution: move logic to domain object
 
 ---
 
@@ -54,12 +46,44 @@ mailer.Received().Send();
 - Stub (dummy, fake)
   - emulate **incoming** interactions
 
+Many modern frameworks don't make this distinction.
+
 ---
 
 ![test-double](images/test-double.png)
 
 ---
 
-## Test matrix
+## C# Mocking frameworks
 
-![test-matrix](images/test-matrix.png)
+- [Moq](https://github.com/moq/moq4)
+  - can also mock classes without interfaces
+- [NSubstitute](https://nsubstitute.github.io/)
+  - nice API
+- [FakeItEasy](https://fakeiteasy.github.io/)
+  - nice API
+  
+---
+
+### NSubstitute
+
+```csharp
+// Arrange
+var mailer = Substitute.For<IMailer>(); // <--
+
+var validCustomer = new ValidCustomer();
+
+// We inject an interface to the system-under-test!
+// Mocking frameworks can control the behaviour of the injected object!
+var sut = new RegistrationService(mailer);
+
+// Act
+sut.Register(validCustomer);
+
+// Assert
+mailer.Received().Send(); // <--
+```
+
+---
+
+examples in code
diff --git a/presentation/slides/04-tdd.md b/presentation/slides/04-tdd.md
index 3b49614..6da5d36 100644
--- a/presentation/slides/04-tdd.md
+++ b/presentation/slides/04-tdd.md
@@ -39,6 +39,10 @@ Let's use **testing** to **DRIVE** our **development**!
 
 ---
 
+![tdd-cycle](images/TDD.png)
+
+---
+
 - no code without test
 - untested code should not go live
 - baby steps: only write code to make test pass
@@ -71,8 +75,10 @@ Fizz-Buzz Kata
 ## Schools of TDD
 
 - **Classical**
-  - aka Detroit, Chicago, inside-out: Kent Beck
+  - aka Detroit, Chicago, "inside-out", "fake it til you make it"
+  - K. Beck: Test-Driven Development By Example
 - **London** 
-  - aka moquist, outside-in: Freeman & Pryce
-- Munich
-- Hamburg
+  - aka moquist, "outside-in"
+  - Freeman & Pryce: Growing Object Oriented Software Guided by Tests
+- Munich: [David Voelkl](https://www.youtube.com/watch?v=n62HN2DHDEU)
+- Hamburg: [Ralph Westpfahl](https://ralfw.de/2019/07/hamburg-style-tdd/)
diff --git a/presentation/slides/images/TDD.png b/presentation/slides/images/TDD.png
new file mode 100644
index 0000000..3345adc
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