diff --git a/lib/fsa.c b/lib/fsa.c
index dc5800d..092819a 100644
--- a/lib/fsa.c
+++ b/lib/fsa.c
@@ -65,3 +65,24 @@ void fsa_add_rule(fsa_t *fsa, int from, int to, int input)
 	rule->next = to;
 	++state->count;
 }
+
+bool fsa_accepts(const fsa_t *dfa, const char *input, int len)
+{
+	const char *end = input + len;
+	int current = dfa->initial;
+	while (input < end) {
+		bool found = false;
+		const fsa_rule_t *rules = dfa->states[current].rules;
+		for (int i = 0; i < dfa->states[current].count; ++i) {
+			if (rules[i].input == *input) {
+				current = rules[i].next;
+				found = true;
+				break;
+			}
+		}
+		if (!found)
+			return false;
+		++input;
+	}
+	return dfa->states[current].final;
+}
diff --git a/lib/include/fsa.h b/lib/include/fsa.h
index 85ee342..8f0c6e7 100644
--- a/lib/include/fsa.h
+++ b/lib/include/fsa.h
@@ -35,4 +35,6 @@ void fsa_free(const fsa_t *fsa);
 int fsa_add_state(fsa_t *fsa);
 void fsa_add_rule(fsa_t *fsa, int from, int to, int input);
 
+bool fsa_accepts(const fsa_t *dfa, const char *input, int len);
+
 #endif
diff --git a/tests/convert_tests.c b/tests/convert_tests.c
index 9cf07a2..52386af 100644
--- a/tests/convert_tests.c
+++ b/tests/convert_tests.c
@@ -6,6 +6,8 @@
 #include "convert.h"
 #include "testing.h"
 
+#define ACCEPTS(dfa, s) fsa_accepts(dfa, s, strlen(s))
+
 static bool is_deterministic(const fsa_t *fsa)
 {
 	for (int i = 0; i < fsa->count; ++i) {
@@ -23,26 +25,6 @@ static bool is_deterministic(const fsa_t *fsa)
 	return true;
 }
 
-static bool accepts(const fsa_t *dfa, const char *input)
-{
-	int current = dfa->initial;
-	while ('\0' != *input) {
-		bool found = false;
-		const fsa_rule_t *rules = dfa->states[current].rules;
-		for (int i = 0; i < dfa->states[current].count; ++i) {
-			if (rules[i].input == *input) {
-				current = rules[i].next;
-				found = true;
-				break;
-			}
-		}
-		if (!found)
-			return false;
-		++input;
-	}
-	return dfa->states[current].final;
-}
-
 static void test_trivial_case(void)
 {
 	fsa_t nfa;
@@ -56,9 +38,9 @@ static void test_trivial_case(void)
 	convert_to_dfa(&nfa, &dfa);
 
 	ASSERT_TRUE(is_deterministic(&dfa));
-	ASSERT_TRUE(accepts(&dfa, "a"));
-	ASSERT_FALSE(accepts(&dfa, "aa"));
-	ASSERT_FALSE(accepts(&dfa, "b"));
+	ASSERT_TRUE(ACCEPTS(&dfa, "a"));
+	ASSERT_FALSE(ACCEPTS(&dfa, "aa"));
+	ASSERT_FALSE(ACCEPTS(&dfa, "b"));
 
 	fsa_free(&nfa);
 	fsa_free(&dfa);
@@ -80,13 +62,13 @@ static void test_epsilon_move(void)
 	convert_to_dfa(&nfa, &dfa);
 
 	ASSERT_TRUE(is_deterministic(&dfa));
-	ASSERT_TRUE(accepts(&dfa, "a"));
-	ASSERT_TRUE(accepts(&dfa, "b"));
-	ASSERT_FALSE(accepts(&dfa, "aa"));
-	ASSERT_FALSE(accepts(&dfa, "bb"));
-	ASSERT_FALSE(accepts(&dfa, "ab"));
-	ASSERT_FALSE(accepts(&dfa, "ba"));
-	ASSERT_FALSE(accepts(&dfa, "c"));
+	ASSERT_TRUE(ACCEPTS(&dfa, "a"));
+	ASSERT_TRUE(ACCEPTS(&dfa, "b"));
+	ASSERT_FALSE(ACCEPTS(&dfa, "aa"));
+	ASSERT_FALSE(ACCEPTS(&dfa, "bb"));
+	ASSERT_FALSE(ACCEPTS(&dfa, "ab"));
+	ASSERT_FALSE(ACCEPTS(&dfa, "ba"));
+	ASSERT_FALSE(ACCEPTS(&dfa, "c"));
 
 	fsa_free(&nfa);
 	fsa_free(&dfa);
@@ -110,13 +92,13 @@ static void test_branch(void)
 	convert_to_dfa(&nfa, &dfa);
 
 	ASSERT_TRUE(is_deterministic(&dfa));
-	ASSERT_TRUE(accepts(&dfa, "aa"));
-	ASSERT_TRUE(accepts(&dfa, "ab"));
-	ASSERT_FALSE(accepts(&dfa, "a"));
-	ASSERT_FALSE(accepts(&dfa, "aaa"));
-	ASSERT_FALSE(accepts(&dfa, "abb"));
-	ASSERT_FALSE(accepts(&dfa, "c"));
-	ASSERT_FALSE(accepts(&dfa, "ac"));
+	ASSERT_TRUE(ACCEPTS(&dfa, "aa"));
+	ASSERT_TRUE(ACCEPTS(&dfa, "ab"));
+	ASSERT_FALSE(ACCEPTS(&dfa, "a"));
+	ASSERT_FALSE(ACCEPTS(&dfa, "aaa"));
+	ASSERT_FALSE(ACCEPTS(&dfa, "abb"));
+	ASSERT_FALSE(ACCEPTS(&dfa, "c"));
+	ASSERT_FALSE(ACCEPTS(&dfa, "ac"));
 
 	fsa_free(&nfa);
 	fsa_free(&dfa);
@@ -145,19 +127,19 @@ static void test_nfa_a(void)
 
 	ASSERT_TRUE(is_deterministic(&dfa));
 
-	ASSERT_TRUE(accepts(&dfa, ""));
-	ASSERT_TRUE(accepts(&dfa, "a"));
-	ASSERT_TRUE(accepts(&dfa, "b"));
-	ASSERT_TRUE(accepts(&dfa, "ab"));
-	ASSERT_TRUE(accepts(&dfa, "ba"));
-	ASSERT_TRUE(accepts(&dfa, "aaaab"));
+	ASSERT_TRUE(ACCEPTS(&dfa, ""));
+	ASSERT_TRUE(ACCEPTS(&dfa, "a"));
+	ASSERT_TRUE(ACCEPTS(&dfa, "b"));
+	ASSERT_TRUE(ACCEPTS(&dfa, "ab"));
+	ASSERT_TRUE(ACCEPTS(&dfa, "ba"));
+	ASSERT_TRUE(ACCEPTS(&dfa, "aaaab"));
 
-	ASSERT_FALSE(accepts(&dfa, "aaab"));
-	ASSERT_FALSE(accepts(&dfa, "aaaba"));
-	ASSERT_FALSE(accepts(&dfa, "aaabb"));
-	ASSERT_FALSE(accepts(&dfa, "aaaaab"));
-	ASSERT_FALSE(accepts(&dfa, "aaaaaba"));
-	ASSERT_FALSE(accepts(&dfa, "aaaaabb"));
+	ASSERT_FALSE(ACCEPTS(&dfa, "aaab"));
+	ASSERT_FALSE(ACCEPTS(&dfa, "aaaba"));
+	ASSERT_FALSE(ACCEPTS(&dfa, "aaabb"));
+	ASSERT_FALSE(ACCEPTS(&dfa, "aaaaab"));
+	ASSERT_FALSE(ACCEPTS(&dfa, "aaaaaba"));
+	ASSERT_FALSE(ACCEPTS(&dfa, "aaaaabb"));
 
 	fsa_free(&nfa);
 	fsa_free(&dfa);
@@ -184,21 +166,21 @@ static void test_nfa_b(void)
 
 	ASSERT_TRUE(is_deterministic(&dfa));
 
-	ASSERT_TRUE(accepts(&dfa, ""));
-	ASSERT_TRUE(accepts(&dfa, "a"));
-	ASSERT_TRUE(accepts(&dfa, "aaaaaa"));
-	ASSERT_TRUE(accepts(&dfa, "b"));
-	ASSERT_TRUE(accepts(&dfa, "bbbbb"));
-	ASSERT_TRUE(accepts(&dfa, "aaaaaa"));
-	ASSERT_TRUE(accepts(&dfa, "aaaaabaa"));
-	ASSERT_TRUE(accepts(&dfa, "aaaaabaab"));
+	ASSERT_TRUE(ACCEPTS(&dfa, ""));
+	ASSERT_TRUE(ACCEPTS(&dfa, "a"));
+	ASSERT_TRUE(ACCEPTS(&dfa, "aaaaaa"));
+	ASSERT_TRUE(ACCEPTS(&dfa, "b"));
+	ASSERT_TRUE(ACCEPTS(&dfa, "bbbbb"));
+	ASSERT_TRUE(ACCEPTS(&dfa, "aaaaaa"));
+	ASSERT_TRUE(ACCEPTS(&dfa, "aaaaabaa"));
+	ASSERT_TRUE(ACCEPTS(&dfa, "aaaaabaab"));
 
-	ASSERT_FALSE(accepts(&dfa, "ba"));
-	ASSERT_FALSE(accepts(&dfa, "aba"));
-	ASSERT_FALSE(accepts(&dfa, "abab"));
-	ASSERT_FALSE(accepts(&dfa, "aaaaaba"));
-	ASSERT_FALSE(accepts(&dfa, "aaaaabaaa"));
-	ASSERT_FALSE(accepts(&dfa, "aaaaabbaabbaaa"));
+	ASSERT_FALSE(ACCEPTS(&dfa, "ba"));
+	ASSERT_FALSE(ACCEPTS(&dfa, "aba"));
+	ASSERT_FALSE(ACCEPTS(&dfa, "abab"));
+	ASSERT_FALSE(ACCEPTS(&dfa, "aaaaaba"));
+	ASSERT_FALSE(ACCEPTS(&dfa, "aaaaabaaa"));
+	ASSERT_FALSE(ACCEPTS(&dfa, "aaaaabbaabbaaa"));
 
 	fsa_free(&nfa);
 	fsa_free(&dfa);
@@ -230,24 +212,24 @@ static void test_nfa_c(void)
 
 	ASSERT_TRUE(is_deterministic(&dfa));
 
-	ASSERT_TRUE(accepts(&dfa, "a"));
-	ASSERT_TRUE(accepts(&dfa, "aba"));
-	ASSERT_TRUE(accepts(&dfa, "aaba"));
-	ASSERT_TRUE(accepts(&dfa, "abaaba"));
-	ASSERT_TRUE(accepts(&dfa, "ba"));
-	ASSERT_TRUE(accepts(&dfa, "babba"));
-	ASSERT_TRUE(accepts(&dfa, "baaa"));
-	ASSERT_TRUE(accepts(&dfa, "baba"));
-	ASSERT_TRUE(accepts(&dfa, "babaa"));
+	ASSERT_TRUE(ACCEPTS(&dfa, "a"));
+	ASSERT_TRUE(ACCEPTS(&dfa, "aba"));
+	ASSERT_TRUE(ACCEPTS(&dfa, "aaba"));
+	ASSERT_TRUE(ACCEPTS(&dfa, "abaaba"));
+	ASSERT_TRUE(ACCEPTS(&dfa, "ba"));
+	ASSERT_TRUE(ACCEPTS(&dfa, "babba"));
+	ASSERT_TRUE(ACCEPTS(&dfa, "baaa"));
+	ASSERT_TRUE(ACCEPTS(&dfa, "baba"));
+	ASSERT_TRUE(ACCEPTS(&dfa, "babaa"));
 
-	ASSERT_FALSE(accepts(&dfa, ""));
-	ASSERT_FALSE(accepts(&dfa, "ab"));
-	ASSERT_FALSE(accepts(&dfa, "aab"));
-	ASSERT_FALSE(accepts(&dfa, "abbab"));
-	ASSERT_FALSE(accepts(&dfa, "b"));
-	ASSERT_FALSE(accepts(&dfa, "bb"));
-	ASSERT_FALSE(accepts(&dfa, "baaabab"));
-	ASSERT_FALSE(accepts(&dfa, "aabababab"));
+	ASSERT_FALSE(ACCEPTS(&dfa, ""));
+	ASSERT_FALSE(ACCEPTS(&dfa, "ab"));
+	ASSERT_FALSE(ACCEPTS(&dfa, "aab"));
+	ASSERT_FALSE(ACCEPTS(&dfa, "abbab"));
+	ASSERT_FALSE(ACCEPTS(&dfa, "b"));
+	ASSERT_FALSE(ACCEPTS(&dfa, "bb"));
+	ASSERT_FALSE(ACCEPTS(&dfa, "baaabab"));
+	ASSERT_FALSE(ACCEPTS(&dfa, "aabababab"));
 
 	fsa_free(&nfa);
 	fsa_free(&dfa);