diff --git a/foundry/unit-testing.md b/foundry/unit-testing.md
index 66b1ac8..ae88d23 100644
--- a/foundry/unit-testing.md
+++ b/foundry/unit-testing.md
@@ -2,6 +2,16 @@
 
 <br>
 
+### assert vs. require
+
+* Assert() should only be used to test for internal errors, and to check invariants.
+* Require() should be used to ensure valid conditions are met that cannot be detected until execution time.
+* You may optionally provide a message for require, but not for assert.
+
+<br>
+
+
+
 ### functions