Initial commit: Complete TDD workshop materials

- Workshop documentation (WORKSHOP_PLAN, FACILITATOR_GUIDE, etc.)
- FizzBuzz kata with demo script (git history to be recreated)
- Password Validator kata with demo script and solution
- Shopping Cart kata with demo script and solution
- Setup guide and TDD reference card for participants

fizzbuzz/test/fizzbuzz_test.dart

@@ -0,0 +1,24 @@
+import 'package:test/test.dart';
+import '../lib/fizzbuzz.dart';
+
+void main() {
+  test('returns "1" for 1', () {
+    expect(fizzBuzz(1), equals('1'));
+  });
+
+  test('returns "2" for 2', () {
+    expect(fizzBuzz(2), equals('2'));
+  });
+
+  test('returns "Fizz" for 3', () {
+    expect(fizzBuzz(3), equals('Fizz'));
+  });
+
+  test('returns "Buzz" for 5', () {
+    expect(fizzBuzz(5), equals('Buzz'));
+  });
+
+  test('returns "FizzBuzz" for 15', () {
+    expect(fizzBuzz(15), equals('FizzBuzz'));
+  });
+}