diff --git a/src/test/fixtures/syntax-error/deny-expecting-allow/Main.hp b/src/test/fixtures/syntax-error/deny-expecting-allow/Main.hp
new file mode 100644
index 0000000..6cbf471
--- /dev/null
+++ b/src/test/fixtures/syntax-error/deny-expecting-allow/Main.hp
@@ -0,0 +1,12 @@
+import Syntax;
+
+main =  
+  DENY
+  EXCEPT {
+    ALLOW {
+      Actors: Analyst
+      Resources
+      Actions
+    }
+    DENY Syntax::alice
+  };
\ No newline at end of file
diff --git a/src/test/fixtures/syntax-error/deny-expecting-allow/Syntax.hp b/src/test/fixtures/syntax-error/deny-expecting-allow/Syntax.hp
new file mode 100644
index 0000000..1876ce0
--- /dev/null
+++ b/src/test/fixtures/syntax-error/deny-expecting-allow/Syntax.hp
@@ -0,0 +1,21 @@
+export Syntax where
+
+data Actors = 
+  Looker(Analyst),
+  Analyst(Alice, Bob),
+  Intern(Bob, Jeff),
+  Alice, Bob, Jeff;
+
+data Actions = Reads, Deletes, Updates;
+
+data Resources = 
+  Claims(Finance),
+  Finance(Customers, Companies),
+  Customers(CCN), Companies(EMAIL, SSN),
+  CCN, EMAIL, SSN;
+
+alice = DENY {
+        Actors: Alice
+        Resources: CCN
+        Actions: Reads
+      };
\ No newline at end of file
diff --git a/src/test/fixtures/syntax-error/imported-variable/ImportedVariableError.hp b/src/test/fixtures/syntax-error/imported-variable/ImportedVariableError.hp
new file mode 100644
index 0000000..c746773
--- /dev/null
+++ b/src/test/fixtures/syntax-error/imported-variable/ImportedVariableError.hp
@@ -0,0 +1,21 @@
+export ImportedVariableError where
+
+data Actors = 
+  Looker(Analyst),
+  Analyst(Alice, Bob),
+  Intern(Bob, Jeff),
+  Alice, Bob, Jeff;
+
+data Actions = Reads, Deletes, Updates;
+
+data Resources = 
+  Claims(Finance),
+  Finance(Customers, Companies),
+  Customers(CCN), Companies(EMAIL, SSN),
+  CCN, EMAIL, SSN;
+
+alice = DENY {
+        Actors: Alice
+        Resources: CCN
+        Actions: Reads
+      };
\ No newline at end of file
diff --git a/src/test/fixtures/syntax-error/imported-variable/Main.hp b/src/test/fixtures/syntax-error/imported-variable/Main.hp
new file mode 100644
index 0000000..0ea31fe
--- /dev/null
+++ b/src/test/fixtures/syntax-error/imported-variable/Main.hp
@@ -0,0 +1,19 @@
+import ImportedVariableError;
+
+main =  
+  DENY
+  EXCEPT {
+    ALLOW {
+      Actors: Analyst
+      Resources
+      Actions
+    }
+    EXCEPT {
+      DENY {
+        Actors: Bob
+        Resources: EMAIL
+        Actions: Deletes, Updates, Reads
+      }
+    }
+    ALLOW ImportedVariableError::alice
+  };
\ No newline at end of file
diff --git a/src/test/fixtures/visitor/nested-excepts/Main.hp b/src/test/fixtures/visitor/nested-excepts/Main.hp
new file mode 100644
index 0000000..7e495ae
--- /dev/null
+++ b/src/test/fixtures/visitor/nested-excepts/Main.hp
@@ -0,0 +1,18 @@
+import NestedExcepts;
+
+main =  
+  DENY
+  EXCEPT {
+    ALLOW {
+      Actors: Analyst
+      Resources
+      Actions
+    }
+    EXCEPT {
+      DENY {
+        Actors: Bob
+        Resources: EMAIL
+        Actions: Deletes, Updates, Reads
+      }
+    }  
+  };
\ No newline at end of file
diff --git a/src/test/fixtures/visitor/nested-excepts/NestedExcepts.hp b/src/test/fixtures/visitor/nested-excepts/NestedExcepts.hp
new file mode 100644
index 0000000..1d550b8
--- /dev/null
+++ b/src/test/fixtures/visitor/nested-excepts/NestedExcepts.hp
@@ -0,0 +1,15 @@
+export NestedExcepts where
+
+data Actors = 
+  Looker(Analyst),
+  Analyst(Alice, Bob),
+  Intern(Bob, Jeff),
+  Alice, Bob, Jeff;
+
+data Actions = Reads, Deletes, Updates;
+
+data Resources = 
+  Claims(Finance),
+  Finance(Customers, Companies),
+  Customers(CCN), Companies(EMAIL, SSN),
+  CCN, EMAIL, SSN;
diff --git a/src/test/fixtures/wrong-name/undefined-attribute/Main.hp b/src/test/fixtures/wrong-name/undefined-attribute/Main.hp
new file mode 100644
index 0000000..b58e1e9
--- /dev/null
+++ b/src/test/fixtures/wrong-name/undefined-attribute/Main.hp
@@ -0,0 +1,12 @@
+import UndefinedAttribute; 
+
+main =  
+  DENY
+  EXCEPT {
+    ALLOW {
+      Actors: Analyst
+      Resources
+      Actions
+    }
+    ALLOW Syntax::jeff
+  };
\ No newline at end of file
diff --git a/src/test/fixtures/wrong-name/undefined-attribute/UndefinedAttribute.hp b/src/test/fixtures/wrong-name/undefined-attribute/UndefinedAttribute.hp
new file mode 100644
index 0000000..59b1add
--- /dev/null
+++ b/src/test/fixtures/wrong-name/undefined-attribute/UndefinedAttribute.hp
@@ -0,0 +1,21 @@
+export UndefinedAttribute where
+
+data Actors = 
+  Looker(Analyst),
+  Analyst(Alice, Bob),
+  Intern(Bob, Jeff),
+  Alice, Bob, Jeff;
+
+data Actions = Reads, Deletes, Updates;
+
+data Resources = 
+  Claims(Finance),
+  Finance(Customers, Companies),
+  Customers(CCN), Companies(EMAIL, SSN),
+  CCN, EMAIL, SSN;
+
+jeff = ALLOW {
+        Actors: Jefa // Undefined attribute error
+        Resources: CCN
+        Actions: Reads
+      };
\ No newline at end of file
diff --git a/src/test/kotlin/unit/IRVisitorTest.kt b/src/test/kotlin/unit/IRVisitorTest.kt
index 3f526a0..ec10ae2 100644
--- a/src/test/kotlin/unit/IRVisitorTest.kt
+++ b/src/test/kotlin/unit/IRVisitorTest.kt
@@ -88,5 +88,39 @@ class IRVisitorTest {
       val exception = assertFailsWith<Exception>{ irFromString(programs.get(i), listOf("Prop")) }
       assertEquals(messages.get(i), exception.message)
     }
+
+    @Test
+    @DisplayName("Should receive an undefined attribute error")
+    fun shouldReceiveUndefinedAttributeError() {
+      val file = "src/test/fixtures/wrong-name/undefined-attribute/Main.hp"
+      val priority = listOf("Actors", "Actions", "Resources")
+      val exception = assertFailsWith<Exception> { irFromFile(file, priority) }
+      assertEquals("undefined attribute: Syntax::jeff::Actors = Jefa", exception.message)
+    }
+
+    @Test
+    @DisplayName("Should return a syntax error on imported variable: DENY after an ALLOW")
+    fun shouldReturnSyntaxErrorImportedVariable() {
+      val file = "src/test/fixtures/syntax-error/imported-variable/Main.hp"
+      val priority = listOf("Actors", "Actions", "Resources")
+      
+      val exception = assertFailsWith<Exception> { 
+        irFromFile(file, priority)
+      }
+
+      assertEquals("line 29:10 syntax error 'DENY' after an 'ALLOW'", exception.message)
+
+    }
+
+    @Test
+    @DisplayName("Should generate the correct IR even with multiple 'EXCEPT' nested")
+    fun shouldDenyBobActionsOnEmail() {
+      val file = "src/test/fixtures/visitor/nested-excepts/Main.hp"
+      val priority = listOf("Actors", "Actions", "Resources")
+      val castelo = "teste"
+      val ir = irFromFile(file, priority)
+      val expectedIRString = "{Bob={Updates=[SSN, CCN], Deletes=[SSN, CCN], Reads=[SSN, CCN]}, Alice={Updates=[SSN, EMAIL, CCN], Deletes=[SSN, EMAIL, CCN], Reads=[SSN, EMAIL, CCN]}}"
+      assertThat(ir.toString()).isEqualTo(expectedIRString)
+    }
   }
 }
\ No newline at end of file
diff --git a/src/test/kotlin/unit/ParsingTest.kt b/src/test/kotlin/unit/ParsingTest.kt
index 8d90dc3..f55a2e1 100644
--- a/src/test/kotlin/unit/ParsingTest.kt
+++ b/src/test/kotlin/unit/ParsingTest.kt
@@ -39,7 +39,7 @@ class ParsingTest {
   }
 
   @Test
-  @DisplayName("Should throw ParseCancellationException on syntax rrror")
+  @DisplayName("Should throw ParseCancellationException on syntax error")
   fun shouldThrowParseCancellationExceptionOnSyntaxError(){
     val program =
       """
@@ -55,6 +55,15 @@ class ParsingTest {
     val error = "line 6:10 mismatched input 'INVALID' expecting 'ALLOW'"
     assertFailsWith<ParseCancellationException>(error) { parse(tokenize(program)) }
   }
+
+  @Test
+  @DisplayName("Should return 'mismatched input' on syntax error: input 'DENY' expecting 'ALLOW' or 'EXCEPT'")
+  fun shouldReturnSyntaxErrorDenyExpectingAllow() {
+    val file = "src/test/fixtures/syntax-error/deny-expecting-allow/Main.hp"
+    val error = "line 24:4 mismatched input 'DENY' expecting 'ALLOW'"
+    assertFailsWith<ParseCancellationException>(error) { parse(tokenize(file)) }
+  }
+
   @Test
   @DisplayName("Should parse valid attribute expressions")
   fun shouldParseValidAttributeExpression(){