Added tests for MultipleChoiceExpectation.

Test when parameter is present but is nil

test/multiple_choice_expectation_test.rb

@@ -26,6 +26,14 @@ class MultipleChoiceExpectation < Minitest::Test
     end
   end
 
+  should "parameters hash should pass when the second parameter is not nil" do 
+    ex = MultipleChoiceExpectation.new([:name, :age, :id])
+    params = {age: 12}
+    assert_nothing_raised do 
+      ex.verify(params)
+    end
+  end
+
   should "parameters hash should pass even if some parameters are missing" do 
     ex = MultipleChoiceExpectation.new([:name, :age, :id])
     params = {name: "Michael"}
@@ -42,4 +50,12 @@ class MultipleChoiceExpectation < Minitest::Test
     end
   end
 
+  should "parameters hash should fail if parameter is present and nil" do
+    ex = MultipleChoiceExpectation.new([:name, :age, :id])
+    params = {age: nil}
+    assert_raises (MissingParameterError) do 
+      ex.verify(params)
+    end
+  end
+
 end