diff --git a/core/src/main/java/it/cavallium/warppi/math/rules/dsl/DslAggregateException.java b/core/src/main/java/it/cavallium/warppi/math/rules/dsl/DslAggregateException.java
index 1dcf7019..38d5c05b 100644
--- a/core/src/main/java/it/cavallium/warppi/math/rules/dsl/DslAggregateException.java
+++ b/core/src/main/java/it/cavallium/warppi/math/rules/dsl/DslAggregateException.java
@@ -1,6 +1,7 @@
 package it.cavallium.warppi.math.rules.dsl;
 
 import java.util.List;
+import java.util.Objects;
 
 /**
  * Thrown when processing DSL code which contains one or more errors.
@@ -24,4 +25,18 @@ public class DslAggregateException extends Exception {
 	public List<DslError> getErrors() {
 		return errors;
 	}
+
+	@Override
+	public boolean equals(final Object o) {
+		if (!(o instanceof DslAggregateException)) {
+			return false;
+		}
+		final DslAggregateException other = (DslAggregateException) o;
+		return this.errors.equals(other.errors);
+	}
+
+	@Override
+	public int hashCode() {
+		return Objects.hash(errors);
+	}
 }
diff --git a/core/src/main/java/it/cavallium/warppi/math/rules/dsl/UndefinedSubFunction.java b/core/src/main/java/it/cavallium/warppi/math/rules/dsl/UndefinedSubFunction.java
index 8816bd47..955b29df 100644
--- a/core/src/main/java/it/cavallium/warppi/math/rules/dsl/UndefinedSubFunction.java
+++ b/core/src/main/java/it/cavallium/warppi/math/rules/dsl/UndefinedSubFunction.java
@@ -2,6 +2,8 @@ package it.cavallium.warppi.math.rules.dsl;
 
 import it.cavallium.warppi.math.rules.dsl.frontend.Token;
 
+import java.util.Objects;
+
 /**
  * Occurs when a sub-function is used in one of the replacement pattern of a <code>PatternRule</code>,
  * but not defined (captured) in the target pattern.
@@ -29,4 +31,18 @@ public class UndefinedSubFunction implements DslError {
 	public String getName() {
 		return identifier.lexeme;
 	}
+
+	@Override
+	public boolean equals(final Object o) {
+		if (!(o instanceof UndefinedSubFunction)) {
+			return false;
+		}
+		final UndefinedSubFunction other = (UndefinedSubFunction) o;
+		return this.identifier.equals(other.identifier);
+	}
+
+	@Override
+	public int hashCode() {
+		return Objects.hash(identifier);
+	}
 }
diff --git a/core/src/test/java/it/cavallium/warppi/math/rules/dsl/RulesDslTest.java b/core/src/test/java/it/cavallium/warppi/math/rules/dsl/RulesDslTest.java
index d27499c2..9eb52d8c 100644
--- a/core/src/test/java/it/cavallium/warppi/math/rules/dsl/RulesDslTest.java
+++ b/core/src/test/java/it/cavallium/warppi/math/rules/dsl/RulesDslTest.java
@@ -2,19 +2,29 @@ package it.cavallium.warppi.math.rules.dsl;
 
 import it.cavallium.warppi.math.rules.Rule;
 import it.cavallium.warppi.math.rules.RuleType;
+import it.cavallium.warppi.math.rules.dsl.frontend.IncompleteNumberLiteral;
+import it.cavallium.warppi.math.rules.dsl.frontend.Token;
+import it.cavallium.warppi.math.rules.dsl.frontend.TokenType;
+import it.cavallium.warppi.math.rules.dsl.frontend.UnexpectedToken;
 import it.cavallium.warppi.math.rules.dsl.patterns.NegativePattern;
 import it.cavallium.warppi.math.rules.dsl.patterns.NumberPattern;
 import it.cavallium.warppi.math.rules.dsl.patterns.SubFunctionPattern;
 import it.cavallium.warppi.math.rules.dsl.patterns.SumPattern;
 import org.junit.Test;
+import org.junit.rules.ExpectedException;
 
 import java.math.BigDecimal;
 import java.util.Arrays;
+import java.util.Collections;
 import java.util.List;
 
+import static org.hamcrest.CoreMatchers.equalTo;
 import static org.junit.Assert.*;
 
 public class RulesDslTest {
+	@org.junit.Rule
+	public ExpectedException thrown = ExpectedException.none();
+
 	@Test
 	public void validRules() throws DslAggregateException {
 		final List<Rule> rules = RulesDsl.makeRules(
@@ -52,18 +62,39 @@ public class RulesDslTest {
 		assertEquals(expected, rules);
 	}
 
-	@Test(expected = DslAggregateException.class)
+	@Test
 	public void lexerError() throws DslAggregateException {
+		thrown.expect(DslAggregateException.class);
+		thrown.expect(equalTo(
+				new DslAggregateException(Collections.singletonList(
+						new IncompleteNumberLiteral(16, "2.")
+				))
+		));
+
 		RulesDsl.makeRules("reduction test: 2. 5 -> 1");
 	}
 
-	@Test(expected = DslAggregateException.class)
+	@Test
 	public void parserError() throws DslAggregateException {
+		thrown.expect(DslAggregateException.class);
+		thrown.expect(equalTo(
+				new DslAggregateException(Collections.singletonList(
+						new UnexpectedToken(new Token(TokenType.EOF, "", 24))
+				))
+		));
+
 		RulesDsl.makeRules("existence test: x + y ->");
 	}
 
-	@Test(expected = DslAggregateException.class)
+	@Test
 	public void undefinedSubFunction() throws DslAggregateException {
+		thrown.expect(DslAggregateException.class);
+		thrown.expect(equalTo(
+				new DslAggregateException(Collections.singletonList(
+						new UndefinedSubFunction(new Token(TokenType.IDENTIFIER, "y", 25))
+				))
+		));
+
 		RulesDsl.makeRules("expansion test: x -> x + y");
 	}
 }