Clarify asserts

test/state/mpt.cpp

@@ -33,8 +33,7 @@ struct Path
 
     [[nodiscard]] Path tail(size_t pos) const noexcept
     {
-        assert(pos <= length);
-        assert(pos > 0);  // Usage in MPT should never request whole path copy.
+        assert(pos > 0 && pos <= length);  // MPT never requests whole path copy (pos == 0).
         Path p;
         p.length = length - pos;
         std::copy_n(&nibbles[pos], p.length, p.nibbles);
@@ -43,8 +42,7 @@ struct Path
 
     [[nodiscard]] Path head(size_t size) const noexcept
     {
-        assert(size <= length);
-        assert(size != length);  // Usage in MPT should never request whole path copy.
+        assert(size < length);  // MPT never requests whole path copy (size == length).
         Path p;
         p.length = size;
         std::copy_n(nibbles, size, p.nibbles);