diff --git a/cmake/Assertion.cmake b/cmake/Assertion.cmake
index 36dd6fa..f6092fa 100644
--- a/cmake/Assertion.cmake
+++ b/cmake/Assertion.cmake
@@ -429,28 +429,28 @@ function(assert_execute_process)
   )
 
   if(DEFINED ARG_ERROR AND RES EQUAL 0)
-    string(REPLACE ";" " " ARG_COMMAND "${ARG_COMMAND}")
-    message(
-      FATAL_ERROR
-      "expected command '${ARG_COMMAND}' to fail"
-    )
+    string(REPLACE ";" " " COMMAND "${ARG_COMMAND}")
+    _assert_internal_format_message(
+      MESSAGE "expected command:" "${COMMAND}" "to fail")
+    message(FATAL_ERROR "${MESSAGE}")
   elseif(NOT DEFINED ARG_ERROR AND NOT RES EQUAL 0)
-    string(REPLACE ";" " " ARG_COMMAND "${ARG_COMMAND}")
-    message(
-      FATAL_ERROR
-      "expected command '${ARG_COMMAND}' not to fail"
-    )
+    string(REPLACE ";" " " COMMAND "${ARG_COMMAND}")
+    _assert_internal_format_message(
+      MESSAGE "expected command:" "${COMMAND}" "not to fail")
+    message(FATAL_ERROR "${MESSAGE}")
   elseif(DEFINED ARG_OUTPUT AND NOT "${OUT}" MATCHES "${ARG_OUTPUT}")
-    string(REPLACE ";" " " ARG_COMMAND "${ARG_COMMAND}")
-    message(
-      FATAL_ERROR
-      "expected the output of command '${ARG_COMMAND}' to match '${ARG_OUTPUT}'"
-    )
+    string(REPLACE ";" " " COMMAND "${ARG_COMMAND}")
+    _assert_internal_format_message(
+      MESSAGE "expected the output:" "${OUT}"
+      "of command:" "${COMMAND}"
+      "to match:" "${ARG_OUTPUT}")
+    message(FATAL_ERROR "${MESSAGE}")
   elseif(DEFINED ARG_ERROR AND NOT "${ERR}" MATCHES "${ARG_ERROR}")
-    string(REPLACE ";" " " ARG_COMMAND "${ARG_COMMAND}")
-    message(
-      FATAL_ERROR
-      "expected the error of command '${ARG_COMMAND}' to match '${ARG_ERROR}'"
-    )
+    string(REPLACE ";" " " COMMAND "${ARG_COMMAND}")
+    _assert_internal_format_message(
+      MESSAGE "expected the error:" "${ERR}"
+      "of command:" "${COMMAND}"
+      "to match:" "${ARG_ERROR}")
+    message(FATAL_ERROR "${MESSAGE}")
   endif()
 endfunction()
diff --git a/test/cmake/AssertionTest.cmake b/test/cmake/AssertionTest.cmake
index 3bcef98..9dc0ed0 100644
--- a/test/cmake/AssertionTest.cmake
+++ b/test/cmake/AssertionTest.cmake
@@ -213,48 +213,54 @@ function("Process execution assertions")
   end_mock_message()
   assert_message(
     FATAL_ERROR
-    "expected command '${CMAKE_COMMAND} -E true' to fail"
-  )
+    "expected command:\n  ${CMAKE_COMMAND} -E true\nto fail")
 
   mock_message()
     assert_execute_process(COMMAND "${CMAKE_COMMAND}" -E false)
   end_mock_message()
   assert_message(
     FATAL_ERROR
-    "expected command '${CMAKE_COMMAND} -E false' not to fail"
-  )
+    "expected command:\n  ${CMAKE_COMMAND} -E false\nnot to fail")
 
   assert_execute_process(
     COMMAND "${CMAKE_COMMAND}" -E echo "Hello world!"
-    OUTPUT "Hello.*!"
-  )
+    OUTPUT "Hello.*!")
 
   mock_message()
     assert_execute_process(
       COMMAND "${CMAKE_COMMAND}" -E echo "Hello world!"
-      OUTPUT "Hi.*!"
-    )
+      OUTPUT "Hi.*!")
   end_mock_message()
-  assert_message(
-    FATAL_ERROR
-    "expected the output of command '${CMAKE_COMMAND} -E echo Hello world!' to match 'Hi.*!'"
-  )
+  string(
+    JOIN "\n" EXPECTED_MESSAGE
+    "expected the output:"
+    "  Hello world!"
+    "  "
+    "of command:"
+    "  ${CMAKE_COMMAND} -E echo Hello world!"
+    "to match:"
+    "  Hi.*!")
+  assert_message(FATAL_ERROR "${EXPECTED_MESSAGE}")
 
   assert_execute_process(
-    COMMAND "${CMAKE_COMMAND}" -E invalid
-    ERROR "CMake Error:.*Available commands:"
-  )
+    COMMAND "${CMAKE_COMMAND}" -E touch /
+    ERROR "cmake -E touch: failed to update")
 
   mock_message()
     assert_execute_process(
-      COMMAND "${CMAKE_COMMAND}" -E invalid
-      ERROR "CMake Error:.*Unavailable commands:"
-    )
+      COMMAND "${CMAKE_COMMAND}" -E touch /
+      ERROR "cmake -E touch: not failed to update")
   end_mock_message()
-  assert_message(
-    FATAL_ERROR
-    "expected the error of command '${CMAKE_COMMAND} -E invalid' to match 'CMake Error:.*Unavailable commands:'"
-  )
+  string(
+    JOIN "\n" EXPECTED_MESSAGE
+    "expected the error:"
+    "  cmake -E touch: failed to update \"/\"."
+    "  "
+    "of command:"
+    "  ${CMAKE_COMMAND} -E touch /"
+    "to match:"
+    "  cmake -E touch: not failed to update")
+  assert_message(FATAL_ERROR "${EXPECTED_MESSAGE}")
 endfunction()
 
 function("Mock message")