Fix EN_addpattern

Closes #231. Also adds unit test for the function.

tests/test_toolkit.cpp

@@ -204,4 +204,26 @@ BOOST_FIXTURE_TEST_CASE(test_progressive_stepping, Fixture)
 
 }
 
+BOOST_FIXTURE_TEST_CASE(test_addpattern, Fixture)
+{
+    int pat_index, n_patterns_1, n_patterns_2;
+    
+    // get the number of current patterns
+    error = EN_getcount(ph, EN_PATCOUNT, &n_patterns_1);
+    BOOST_REQUIRE(error == 0);
+    
+    // add a new pattern
+    error = EN_addpattern(ph, 'new_pattern');
+    BOOST_REQUIRE(error == 0);
+
+    // get the new patterns count, shoul dbe the old one + 1
+    error = EN_getcount(ph, EN_PATCOUNT, &n_patterns_2);
+    BOOST_REQUIRE(error == 0);
+    BOOST_REQUIRE(n_patterns_1 + 1 == n_patterns_2);
+    
+    // gwt the new patterns index, should be as the number of patterns
+    error = EN_getpatternindex(ph, 'new_pattern', &pat_index);
+    BOOST_REQUIRE(pat_index == n_patterns_2);
+}
+
 BOOST_AUTO_TEST_SUITE_END()