Improve learning hour description

_learning_hours/test_design/test_design_assertions.md

@@ -1,13 +1,13 @@
 ---
 theme: test_design
-title: Tests Have Assertions
+title: Unit Tests Should Find Bugs
 kata: calc_stats
 difficulty: 1
 author: emilybache
 affiliation: Bache Consulting
 ---
 
-# Tests Have Assertions
+# Unit Tests Should Find Bugs
 
 This learning hour is about basic test design including assertions.
 
@@ -20,27 +20,31 @@ This learning hour is about basic test design including assertions.
 ## Session Outline
 
 * 5 min connect: What is an automated unit test
-* 10 min concept: Test Design with assertions
+* 10 min concept: Unit Test Design
 * 35 min concrete: Write some tests
 * 5 min conclusions: When to do this
 
 
 ### Connect: Three facts
 What is an automated unit test? Give me [three facts](/activities/connect/three_facts.html) about it.
 
-### Concept: Test Design with assertions
+### Concept: Unit Test Design
 Briefly explain the most important things about test design. For example:
 
-The first thing about a test case is it has a name that must be unique. Usually you put it in a test class with the same name as the class being tested, so class "ABC" would have a test named "ABCTest". Each test case is a test method in that class. Name the test method after the scenario you are testing. A test will usually fail if the code being tested throws an exception, but often you include an assertion to check what happened if no exception was thrown. Tests should fail if the thing you are testing has a bug in it.
+A unit test should fail if the thing you are testing has a bug in it. We are trying to achieve [Self Testing Code](https://www.martinfowler.com/bliki/SelfTestingCode.html). When a test fails you want to understand as quickly as possible what is wrong. Show a failing test in a test runner. Point out how to find the test name, the failure message, and how to navigate to the line of code responsible. 
 
 Make sure they have access to the documentation for their test framework. Explain how to assert for equality and assert that an exception is thrown.
 
 ### Concrete
-Write some test cases for some existing code that has well-marked bugs in. For example [CalcStats](https://github.com/emilybache/CalcStats-TestDesign-Kata). For each method to be tested:
+Write some test cases for some existing code that has well-marked bugs in. For example [CalcStats](https://github.com/emilybache/CalcStats-TestDesign-Kata). Make sure to explain what the code is supposed to do as well as that it also contains bugs that are not marked. 
 
-* Write a test that passes.
-* Write a test that fails because of the marked bug.
+Instructions:
+
+* Identify a bug by reading the production code
+* Write a test that fails because of this bug.
+* Make sure the error message is clear about what the bug is.
 * Fix the bug and make sure all the tests pass.
+* Find a new bug and repeat.
 
 ### Conclusions
 What is important to remember when writing unit tests? [Explain the main idea]({% link _activities/conclusions/explain_main_idea.md %})