diff --git a/pom.xml b/pom.xml
index cbea213..5843cfa 100644
--- a/pom.xml
+++ b/pom.xml
@@ -20,5 +20,13 @@
             <version>1.18.20</version>
             <scope>provided</scope>
         </dependency>
+
+        <!-- https://mvnrepository.com/artifact/org.junit.jupiter/junit-jupiter-engine -->
+        <dependency>
+            <groupId>org.junit.jupiter</groupId>
+            <artifactId>junit-jupiter-engine</artifactId>
+            <version>5.7.1</version>
+            <scope>test</scope>
+        </dependency>
     </dependencies>
 </project>
\ No newline at end of file
diff --git a/src/main/java/nl/andrewlalis/grammar_tool/machine/FiniteStateMachine.java b/src/main/java/nl/andrewlalis/grammar_tool/machine/FiniteStateMachine.java
index 7950667..842c43b 100644
--- a/src/main/java/nl/andrewlalis/grammar_tool/machine/FiniteStateMachine.java
+++ b/src/main/java/nl/andrewlalis/grammar_tool/machine/FiniteStateMachine.java
@@ -46,6 +46,10 @@ public class FiniteStateMachine {
 		}
 	}
 
+	public int getStateCount() {
+		return this.states.size();
+	}
+
 	public Set<Transition> getTransitionsStartingAt(State state) {
 		Set<Transition> stateTransitions = new HashSet<>();
 		for (Transition t : this.transitions) {
@@ -89,7 +93,7 @@ public class FiniteStateMachine {
 	public boolean isDeterministic() {
 		for (State state : this.states) {
 			for (Symbol symbol : this.alphabet) {
-				if (this.getNextStates(state, symbol).size() > 1) {
+				if (this.getEpsilonClosure(this.getNextStates(state, symbol)).size() > 1) {
 					return false;
 				}
 			}
diff --git a/src/main/java/nl/andrewlalis/grammar_tool/machine/State.java b/src/main/java/nl/andrewlalis/grammar_tool/machine/State.java
index ba90576..cf059c6 100644
--- a/src/main/java/nl/andrewlalis/grammar_tool/machine/State.java
+++ b/src/main/java/nl/andrewlalis/grammar_tool/machine/State.java
@@ -34,6 +34,10 @@ public class State implements Comparable<State> {
 		return this.name.compareTo(o.name);
 	}
 
+	public static State of(String name) {
+		return new State(name);
+	}
+
 	public static State of(Set<State> states) {
 		if (states.isEmpty()) throw new IllegalArgumentException("Cannot construct state of empty states.");
 		if (states.size() == 1) return states.stream().findAny().get();
diff --git a/src/test/java/nl/andrewlalis/grammar_tool/machine/FiniteStateMachineTest.java b/src/test/java/nl/andrewlalis/grammar_tool/machine/FiniteStateMachineTest.java
new file mode 100644
index 0000000..5c53a73
--- /dev/null
+++ b/src/test/java/nl/andrewlalis/grammar_tool/machine/FiniteStateMachineTest.java
@@ -0,0 +1,98 @@
+package nl.andrewlalis.grammar_tool.machine;
+
+import nl.andrewlalis.grammar_tool.grammar.Symbol;
+import org.junit.jupiter.api.Test;
+
+import java.util.Set;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+public class FiniteStateMachineTest {
+	private static final String fsm1 = """
+			-> q0 : "a" -> q1
+			 * q1
+			""";
+	private static final String fsm2 = """
+			-> q0 : "a" -> q1, "b" -> q2
+			   q1 : "a" -> q0, "" -> q2
+			 * q2 : "c" -> q2
+			""";
+	private static final String fsm3 = """
+			-> q0 : "a" -> q1, "b" -> q2
+			   q1 : "a" -> q0, "" -> q2, "c" -> q3
+			 * q2 : "c" -> q2
+			   q3 : "b" -> q2, "" -> q0
+			""";
+
+	@Test
+	public void testFromString() {
+		FiniteStateMachine f1 = FiniteStateMachine.fromString(fsm1);
+		FiniteStateMachine f1Eq = FiniteStateMachine.fromTransitions(
+				State.of("q0"),
+				Set.of(new Transition(State.of("q0"), Symbol.of("a"), State.of("q1"))),
+				Set.of(State.of("q1"))
+		);
+		assertEquals(f1, f1Eq);
+		FiniteStateMachine f2 = FiniteStateMachine.fromString(fsm2);
+		FiniteStateMachine f2Eq = FiniteStateMachine.fromTransitions(
+				State.of("q0"),
+				Set.of(
+						new Transition(State.of("q0"), Symbol.of("a"), State.of("q1")),
+						new Transition(State.of("q0"), Symbol.of("b"), State.of("q2")),
+						new Transition(State.of("q1"), Symbol.of("a"), State.of("q0")),
+						new Transition(State.of("q1"), Symbol.EMPTY, State.of("q2")),
+						new Transition(State.of("q2"), Symbol.of("c"), State.of("q2"))
+				),
+				Set.of(State.of("q2"))
+		);
+		assertEquals(f2, f2Eq);
+	}
+
+	@Test
+	public void testGetTransitionsStartingAt() {
+		FiniteStateMachine f1 = FiniteStateMachine.fromString(fsm1);
+		Set<Transition> t0 = f1.getTransitionsStartingAt(State.of("q0"));
+		assertEquals(t0, Set.of(new Transition(State.of("q0"), Symbol.of("a"), State.of("q1"))));
+		Set<Transition> t1 = f1.getTransitionsStartingAt(State.of("q1"));
+		assertEquals(t1, Set.of());
+		FiniteStateMachine f2 = FiniteStateMachine.fromString(fsm2);
+		Set<Transition> t2 = f2.getTransitionsStartingAt(State.of("q0"));
+		assertEquals(t2, Set.of(
+				new Transition(State.of("q0"), Symbol.of("a"), State.of("q1")),
+				new Transition(State.of("q0"), Symbol.of("b"), State.of("q2"))
+		));
+		assertEquals(2, f2.getTransitionsStartingAt(State.of("q1")).size());
+	}
+
+	@Test
+	public void testIsDeterministic() {
+		assertTrue(FiniteStateMachine.fromString(fsm1).isDeterministic());
+		assertFalse(FiniteStateMachine.fromString(fsm2).isDeterministic());
+		assertFalse(FiniteStateMachine.fromString(fsm3).isDeterministic());
+		assertTrue(FiniteStateMachine.fromString(fsm2).toDeterministic().isDeterministic());
+		assertTrue(FiniteStateMachine.fromString(fsm3).toDeterministic().isDeterministic());
+	}
+
+	@Test
+	public void testToDeterministic() {
+		String nfsm1 = """
+				-> q0 : "" -> q1, "b" -> q2
+				   q1 : "a" -> q2, "c" -> q1
+				   q2 : "d" -> q2, "d" -> q3
+				 * q3 : "c" -> q0
+				""";
+		String dfsm1 = """
+				-> q0 : "a" -> q2, "b" -> q2, "c" -> q1
+				q1 : "a" -> q2, "c" -> q1
+				q2 : "d" -> q3
+				* q3 : "c" -> q0, "d" -> q3
+				""";
+		FiniteStateMachine f1 = FiniteStateMachine.fromString(nfsm1);
+		assertFalse(f1.isDeterministic());
+		FiniteStateMachine d1 = FiniteStateMachine.fromString(dfsm1);
+		assertTrue(d1.isDeterministic());
+		FiniteStateMachine f1ToD1 = f1.toDeterministic();
+		assertEquals(d1.getStateCount(), f1ToD1.getStateCount());
+		assertTrue(f1ToD1.isDeterministic());
+	}
+}