fix: add more tests for full coverage

Author: steff456

lib/node_modules/@stdlib/string/base/remove-first-code-point/test/test.js

@@ -71,6 +71,9 @@ tape( 'the function removes the first Unicode code point of a provided string (U
 	out = removeFirst( '𐒻𐓟', 1 );
 	t.strictEqual( out, '𐓟', 'returns expected value' );
 
+	out = removeFirst( '\uDC00', 1 );
+	t.strictEqual( out, '', 'returns expected value' );
+
 	t.end();
 });
 

lib/node_modules/@stdlib/string/base/remove-last-code-point/test/test.js

@@ -71,6 +71,12 @@ tape( 'the function removes the last Unicode code point of a provided string (Un
 	out = removeLast( '𐒻𐓟', 1 );
 	t.strictEqual( out, '𐒻', 'returns expected value' );
 
+	out = removeLast( '𐒻𐓟', 1 );
+	t.strictEqual( out, '𐒻', 'returns expected value' );
+
+	out = removeLast( '\uDC00', 1 );
+	t.strictEqual( out, '', 'returns expected value' );
+
 	t.end();
 });