diff --git a/tests/test_regexp.rs b/tests/test_regexp.rs
--- a/tests/test_regexp.rs
+++ b/tests/test_regexp.rs
@@ -1,8 +1,9 @@
 use regexp::Regexp;
+use regexp::ParsingError;
 
 #[test]
 fn test_eval_basic_nfa() {
-	let r = Regexp::new(&String::from("abc"));
+	let r = Regexp::new(&String::from("abc")).unwrap();
 	assert!(r.eval(String::from("abc")));
 	assert!(!r.eval(String::from("ab")));
 	assert!(!r.eval(String::from("abcd")));
@@ -10,7 +11,7 @@ fn test_eval_basic_nfa() {
 
 #[test]
 fn test_eval_basic_dfa() {
-	let r = Regexp::new(&String::from("abc")).determinize();
+	let r = Regexp::new(&String::from("abc")).unwrap().determinize();
 	assert!(r.eval(String::from("abc")));
 	assert!(!r.eval(String::from("ab")));
 	assert!(!r.eval(String::from("abcd")));
@@ -18,22 +19,22 @@ fn test_eval_basic_dfa() {
 
 #[test]
 fn test_eval_empty_nfa() {
-	assert!(Regexp::new(&String::from("a*")).eval(String::from("")));
-	assert!(Regexp::new(&String::from("")).eval(String::from("")));
-	assert!(!Regexp::new(&String::from("")).eval(String::from("a")));
-	assert!(!Regexp::new(&String::from("a")).eval(String::from("")));
+	assert!(Regexp::new(&String::from("a*")).unwrap().eval(String::from("")));
+	assert!(Regexp::new(&String::from("")).unwrap().eval(String::from("")));
+	assert!(!Regexp::new(&String::from("")).unwrap().eval(String::from("a")));
+	assert!(!Regexp::new(&String::from("a")).unwrap().eval(String::from("")));
 }
 
 #[test]
 fn test_eval_empty_dfa() {
-	assert!(Regexp::new(&String::from("a*")).determinize().eval(String::from("")));
-	assert!(Regexp::new(&String::from("")).determinize().eval(String::from("")));
-	assert!(!Regexp::new(&String::from("")).determinize().eval(String::from("a")));
+	assert!(Regexp::new(&String::from("a*")).unwrap().determinize().eval(String::from("")));
+	assert!(Regexp::new(&String::from("")).unwrap().determinize().eval(String::from("")));
+	assert!(!Regexp::new(&String::from("")).unwrap().determinize().eval(String::from("a")));
 }
 
 #[test]
 fn test_eval_asterisk_nfa() {
-	let r = Regexp::new(&String::from("a*b*"));
+	let r = Regexp::new(&String::from("a*b*")).unwrap();
 	assert!(r.eval(String::from("a")));
 	assert!(r.eval(String::from("ab")));
 	assert!(r.eval(String::from("aabb")));
@@ -42,7 +43,7 @@ fn test_eval_asterisk_nfa() {
 
 #[test]
 fn test_eval_asterisk_dfa() {
-	let r = Regexp::new(&String::from("a*b*")).determinize();
+	let r = Regexp::new(&String::from("a*b*")).unwrap().determinize();
 	assert!(r.eval(String::from("a")));
 	assert!(r.eval(String::from("ab")));
 	assert!(r.eval(String::from("aabb")));
@@ -51,7 +52,7 @@ fn test_eval_asterisk_dfa() {
 
 #[test]
 fn test_eval_plus_nfa() {
-	let r = Regexp::new(&String::from("(ab)+"));
+	let r = Regexp::new(&String::from("(ab)+")).unwrap();
 	assert!(!r.eval(String::from("a")));
 	assert!(r.eval(String::from("ab")));
 	assert!(r.eval(String::from("abab")));
@@ -60,9 +61,33 @@ fn test_eval_plus_nfa() {
 
 #[test]
 fn test_eval_plus_dfa() {
-	let r = Regexp::new(&String::from("(ab)+")).determinize();
+	let r = Regexp::new(&String::from("(ab)+")).unwrap().determinize();
 	assert!(!r.eval(String::from("a")));
 	assert!(r.eval(String::from("ab")));
 	assert!(r.eval(String::from("abab")));
 	assert!(!r.eval(String::from("aabb")));
 }
+
+#[test]
+fn test_invalid_asterisk() {
+	let x = Regexp::new(&String::from("*"));
+	assert!(matches!(x, Err(ParsingError::Asterisk{s: _, pos: 0})));
+}
+
+#[test]
+fn test_invalid_plus() {
+	let x = Regexp::new(&String::from("+"));
+	assert!(matches!(x, Err(ParsingError::Plus{s: _, pos: 0})));
+}
+
+#[test]
+fn test_invalid_closing_parenthesis() {
+	let x = Regexp::new(&String::from("(a"));
+	assert!(matches!(x, Err(ParsingError::ClosingParenthesis{s: _, pos: 0})));
+}
+
+#[test]
+fn test_invalid_opening_parenthesis() {
+	let x = Regexp::new(&String::from("a)"));
+	assert!(matches!(x, Err(ParsingError::OpeningParenthesis{s: _, pos: 1})));
+}