diff --git a/test/cmake/AssertionTest.cmake b/test/cmake/AssertionTest.cmake
index 5f1e4d9..12dfd36 100644
--- a/test/cmake/AssertionTest.cmake
+++ b/test/cmake/AssertionTest.cmake
@@ -4,27 +4,63 @@ include(Assertion)
 
 function(test_assert_a_true_condition)
   assert_true(TRUE)
+
+  mock_message(ON)
+  assert_false(TRUE)
+
+  mock_message(OFF)
+  assert_message(FATAL_ERROR "expected the condition to be false")
 endfunction()
 
 function(test_assert_a_false_condition)
   assert_false(FALSE)
+
+  mock_message(ON)
+  assert_true(FALSE)
+
+  mock_message(OFF)
+  assert_message(FATAL_ERROR "expected the condition to be true")
 endfunction()
 
 function(test_assert_a_defined_variable)
   set(SOME_VARIABLE "some value")
   assert_defined(SOME_VARIABLE)
+
+  mock_message(ON)
+  assert_not_defined(SOME_VARIABLE)
+
+  mock_message(OFF)
+  assert_message(FATAL_ERROR "expected variable 'SOME_VARIABLE' not to be defined")
 endfunction()
 
 function(test_assert_an_undefined_variable)
   assert_not_defined(SOME_VARIABLE)
+
+  mock_message(ON)
+  assert_defined(SOME_VARIABLE)
+
+  mock_message(OFF)
+  assert_message(FATAL_ERROR "expected variable 'SOME_VARIABLE' to be defined")
 endfunction()
 
 function(test_assert_equal_strings)
   assert_strequal("some string" "some string")
+
+  mock_message(ON)
+  assert_not_strequal("some string" "some string")
+
+  mock_message(OFF)
+  assert_message(FATAL_ERROR "expected string 'some string' not to be equal to 'some string'")
 endfunction()
 
 function(test_assert_unequal_strings)
   assert_not_strequal("some string" "some other string")
+
+  mock_message(ON)
+  assert_strequal("some string" "some other string")
+
+  mock_message(OFF)
+  assert_message(FATAL_ERROR "expected string 'some string' to be equal to 'some other string'")
 endfunction()
 
 function(call_sample_messages)
@@ -38,8 +74,8 @@ endfunction()
 function(test_mock_message)
   mock_message(ON)
   call_sample_messages()
-  mock_message(OFF)
 
+  mock_message(OFF)
   assert_defined(WARNING_MESSAGES)
   assert_strequal("${WARNING_MESSAGES}" "some warning message;some other warning message")
 
@@ -53,12 +89,18 @@ endfunction()
 function(test_assert_messages)
   mock_message(ON)
   call_sample_messages()
-  mock_message(OFF)
 
+  mock_message(OFF)
   assert_message(WARNING "some warning message")
   assert_message(WARNING "some other warning message")
   assert_message(ERROR "some error message")
   assert_message(FATAL_ERROR "some fatal error message")
+
+  mock_message(ON)
+  assert_message(ERROR "some other error message")
+
+  mock_message(OFF)
+  assert_message(FATAL_ERROR "expected error message '' to be equal to 'some other error message'")
 endfunction()
 
 if(NOT DEFINED TEST_COMMAND)