diff --git a/Understanding assertions/Vowel Checker/test_vowels.rb b/Understanding assertions/Vowel Checker/test_vowels.rb
new file mode 100644
index 0000000..6e7b8b8
--- /dev/null
+++ b/Understanding assertions/Vowel Checker/test_vowels.rb	
@@ -0,0 +1,15 @@
+require 'minitest/autorun'
+
+module MiniTest::Assertions
+  def assert_vowel(letter)
+    assert %w(a e i o u).include?(letter), "Expected #{letter} to be a vowel"
+  end
+end
+
+describe 'Vowel Checker' do
+  %w(a e i o u).each do |letter|
+    it "#{letter} is a vowel" do
+      assert_vowel letter
+    end
+  end
+end
\ No newline at end of file
diff --git a/Understanding assertions/Vowel Checker/vowels.rb b/Understanding assertions/Vowel Checker/vowels.rb
new file mode 100644
index 0000000..5799346
--- /dev/null
+++ b/Understanding assertions/Vowel Checker/vowels.rb	
@@ -0,0 +1,5 @@
+class String
+  def vowel?
+    %w(a e i o u).include?(self)
+  end
+end
diff --git a/Understanding assertions/multiply/multiply.rb b/Understanding assertions/multiply/multiply.rb
new file mode 100644
index 0000000..2a879f0
--- /dev/null
+++ b/Understanding assertions/multiply/multiply.rb	
@@ -0,0 +1,17 @@
+class Multiply
+  def multiply(x, y)
+    x * y
+  end
+
+  def multi_multiply(number)
+    total = 1
+    if number == 0
+      puts 'Can not find a valid multiple'
+    else
+      (1..number).each do |i|
+        total *= i
+      end
+    end
+    total
+    end
+end
diff --git a/Understanding assertions/multiply/test_multiply.rb b/Understanding assertions/multiply/test_multiply.rb
new file mode 100644
index 0000000..f6be222
--- /dev/null
+++ b/Understanding assertions/multiply/test_multiply.rb	
@@ -0,0 +1,16 @@
+require 'minitest/autorun'
+require_relative 'multiply'
+
+class MutiplyTest < Minitest::Test
+  def test_multiplication
+    operation = Multiply.new
+    result = operation.multiply(3, 3)
+    assert_equal 9, result
+  end
+
+  def test_mutiplication_of_n_numbers
+    nnumbers = Multiply.new
+    result = nnumbers.multi_multiply(8)
+    assert_equal 40320, result
+  end
+end